A Broadcast Engineering TH-cam channel. How cool! I was a contract engineer/staff engineer/chief engineer for a little over twenty years with a dozen stations in the southeast. Finally got tired of being on call all the time (even when my name wasn't on the board) so I became an IT geek, and spent the next fifteen years crawling under desks. Retired now, and enjoying Ham radio. Thank you for the memories! 4:08 Please take a look at the Dewalt DCF680 cordless screwdriver. It'll save your wrists from repetitive stress injury, save time, and is about as likely to overtorque or cam out as a manual screwdriver. Not useful for heavy stuff like 2 1/2" wood screws, but great for racks or the rivet nuts on PA cabinets. Gyro controlled, so just a little twist in the direction starts tightening or loosening, more twist goes faster. There's a clutch, but it's unnecessary since you can hold it like a manual screwdriver.
Also, remember that your PA tuning will be slightly different between the antenna and the dummy load. Best to tune into the antenna. Dip the plate, peak the grid. On that Harris FM, tune for peak RF TPO. You will notice that the PA tune and load peaks are pretty wide, so skew to the side of the peak that gives lower PA current. That is tuned.
As a new to the game contract engineer I found this troubleshooting exercise very valuable. Would have really liked to see it go to final fix! Maybe a pt 2?
Many moons ago I maintained a RCA-BTF-20E. It was a pretty good box except for the strip-line tuning- the sliding finger-stock would arc and burn when tuning and the RF-voltage on the 4CX15000 PA plate was very high. A number of them were known to arc and set insulator shelf on fire.
Ours ran as a backup until 2016 when we donated it to a museum. Those were fun when the lamp in the VSWR meter burned out and they'd dump the plate until you figured it out.
Thanks for your reply. I didn't see any covering on the grounding cable. Guess I'll have to look closer next time. Stay safe because those caps do bite. :>)
I just discovered your channel. I am a TV/radio engineer as well who also started a TH-cam channel. I will have to try something like this when I do an amplifier swap on a Nautel transmitter, which is something I plan on doing very soon.
I was looking at how close the back of that transmitter was to the wall. They're usually installed so there's just enough space to swing the back door open. That causes a major problem; you will have one injury turn into three. If you're in back of the transmitter and touch something that's still slightly energized, you'll burn the tips of your fingers. When you do that, you'll jerk your arm back and slam your elbow into the wall behind you. Immediately after that, you'll pull your arm forward again sharply and slam your nuckles into something inside the transmitter. Thus, one injury turns quickly into three! Our station engineer told me this story one night when I was in my late teens and working my first job (weekends) in radio. He and I were at the transmitter one night while he was repairing something. We both had a good laugh at it, but in my experiences, it's turned out to be nearly true! That engineer is in his late 80's now and we still laugh about it.
Used to work on commercial AM,FM, and analog TV transmitters. What I see here is very familiar to me. For the past 35 yrs and ongoing work on 250kw and 500 kw SW transmitters for VOA and Radio Marti( they broadcast to Cuba) The site is the only remaining Greenville,NC.plants A site and C site are closed C plant building is used by ECU and is their property(state,county) B plant where I am now is Radio Marti. The hv for the tubes is actually similar to what this commercial transmitter has-but VOA tubes run at much higher current.25A 12kv 250kw 16kv 55A for 500kw. As I typed this “don’t bypass interlocks on transmitters” years ago an engineer was KILLED from the bypass. The tubes used at our plant are water and vapor cooled. In older 250kw GE SW transmitters the RF driver feeding the PA is 50kw. Newer transmitters here have 2 power stages-not 3 as the older GE uses. Also SW transmitters are variable frequency. At the SW plant you tune transmitters several times a shift-each frequency change. This does cause mechanical wear on components. And of course the ground hook is your friend! USE THEM! Filament voltage on one of the VOA tubes is 14v-but over2000A-rectified filament supply! Rectifier diodes mounted on water cooled heatsinks.
The 4CX250B is the baby of the family. But they work very well in amateur radio amplifiers, typically in push-pull pairs in VHF service. Of course they work well on lower frequencies, too. But if you are interested in doing moon bounce, a pair of those 4CX250s are a good choice. 73 from Bob, WA6WHT ☺️
Aye, when I started in the hobby I bought a set to make my own amplifier, never got it finished though due to.. well... life happened. Still have them somewhere in the storage. 73 de Soren OZ2AEV
I think ur discoloration is just cooked dust. Not that there isn’t an issue but it’s definitely no indication of a bad tube, just that she getting hyot
CPI Data Sheet for the 4CX20,000C shows 13kV as Absolute Maximum for a Class C Amp, grid driven. So, Harris (Gates Air) is just under the Max with 12.7kV on the Factory Test Data sheet but doesn't leave any wiggle room for when the tube starts getting a little weak & needs a little more Plate & Screen Voltage. I have switched to all Nautel transmitters at the sites I maintain.
The 4CX20000 family is rated at a max plate voltage of 10Kv, typical run at 9K. Running them at 14Kv has a high risk of flash over and ruining the tube. I mean yea what's $10k here or there. You have something wrong with the power supply or regulator circuit in that transmitter which should be fixed before further abusing that tube.
The factory test data calls for 12.7kV. 14 is still high, but I don't think GatesAir would tell a customer to run this tube at over 10kV if they didn't think it could handle that plate voltage.
13 KV on the plate? That is generating x-rays. Be careful, men. I have an HT-30 (28 KW TPO) that runs 9 KV on the plate and has 81% PA efficiency. You might want to re-tap that HV supply.
Trust me, broadcast engineers, know that broadcast engineers, get cancer, or at least they used to when they had to tweak the exciter by reaching around the tube in the cabinet
@GWDLABS The copper (they are usually silver plated) fingers are to stop RF leakage. That does not stop x-rays. X-rays are much shorter wavelengths and go through those little cracks. Most of the x-rays are contained within the cabinet when everything is closed up properly. However, there are times when troubleshooting that you have to bypass an interlock or color outside the lines. I've been a broadcast engineer for 39 years and seen it all. Once in the late 90's, I was Chief Engineer of 17 stations all by myself, no help. Now I only have 7 stations.
Nice clean professional installation. Good for you guys! Thanks for the look inside. 🙂 Curious..What's the plate voltage on the RF output tube in the final of that xmit.? Right you just said 13k...LOL nevermind. Tubes run at high voltages whoa! Very different from the modular ones. Power companies love the older stuff, Right? Do you guys keep a spare on hand? Must cost a small fortune.
It sounds like it need to be re tuned the plate and check the loading as well. The VSWR is sending too much power back into the tube causing it to over heat.
As I recall, their VSWR was 1.08 to 1. That's not bad. But there are some things to be concerned about there, like that Plate Voltage. It seems a bit high to me. And possibly the cavity tuning may be a bit off, too, so that 4CX20,000C was dissipating a bit more than necessary for the rated power output. There are good ways to observe that with a spectrum analyzer, which curiously I don't recall seeing anywhere in the video. Around transmitters like these, a spectrum analyzer is a very useful tool. 73 from Bob, WA6WHT and transmitter engineer for several San Francisco Bay Area TV stations at various times. 😀
When using the grounding stick, why do you allow your hand to be on the grounding cable. Not good in my book as one day, you just may feel that cap going to ground. Just asking.
I am wondering what the filament voltage on the tube you mentioned and are the filaments AC or DC I think you said the tube was 4CX20000. I have just found your channel and the other channel I watch is Geerling engineering which give insight into the Broadcast industry.
For the 4CX20000C tube used in this rig, nominal filament voltage is 10VDC at approximately 140 amps. GatesAir recommends lowering the filament to around 9 volts after about 150 hours of use to keep the tube from going “soft” too quickly. That was never done to this one and so we’ll probably need to replace it soon.
@@BroadcastBlueprint Consider getting a copy of the classic book on the subject, titled "The Care and Feeding of Power Grid Tubes" by Eimac. They explained a lot about filament management to get the longest life and best performance out of vacuum tubes like that 4CX20,000C. I believe it is available as a PDF as well as in hard copy. As I recall, the PDF was free. I also recommend getting a copy of the data sheet for that 4CX20,000C, so you can see both what the ratings of it are, and also what typical operation as a Class C FM power amplifier looks like About that exhaust air temperature, it seems a bit high to me, but I am more familiar with the 3XC10,000A7 triode running in low band VHF TV visual amplifier service, which means they were running AB1 or AB2 as grounded grid linear amplifiers. But our exhaust air temperature was around 135 degrees F with inlet air of 65 degrees F, so we had a 70 degree delta between inlet and outlet air temperature. And we checked our air filters with a vacuum gauge calibrated in inches of water. Too much drop across the air filters was the reason to replace them because a plugged up air filter can reduce the air flow through the anode of the tube and the cooling of the socket, as well. Higher temperatures lead to grief sooner. Also when you pull the tube, take a very good look at the contact fingers in the socket. One point of failure is weak fingers that lead to higher resistance contacts with that tube. 140 amps at 10 volts can cause some serious finger heating if they are not all making good contact with the tube base. Anyway I liked your video, although a chest mounted camera might have shown some of what you were doing a bit better than the helmet mounted camera did. 73 from WA6WHT, transmitter engineer for KTEH-TV54 and KSTS-TV48, San Jose, and KRON-TV4, and KTSF-TV26, San Francisco. I didn't do all of those rigs at once, however.! ☺️
Yes! Those are compressed nitrogen cylinders. We connect them to a dehydrator/compressor unit that maintains pressure inside the coaxial transmission line. Nitrogen is a very popular dielectric gas that prevents the center conductor from arcing over to the outer shield and also keeps moisture out of the line.
No Safety Officer ? It's a good practice to have a Safety Officer who is on scene of any potentially dangerous work. They observe and tell you if they notice something but also stay out of the danger zone and are there to call for help if someone becomes downed. They also take readings of RF radiation during the work and log reports for each employee and their radiation exposure. At NL Industries the Safety Officer kept the logs for each piece of equipment and the total radiation daily and over time for the equipment and each employee. If an employee was nearing their legal limit of exposure the Safety Officer would put in a request for transfer for the employee so they would not receive any more radiation for the year. In real bad cases they had people who were given desk jobs or even paid time off.
All the radiation, with very minor exceptions, is non-izoning. The transmitter manufacturer has responsibility for the inherent safety of the device. As far as a safety officer, the chief is there and is hands-on supervising the process.
As an Electrician, I think one of the reasons why that FM broadcast station has so much grounding is because of NEC article 250. Just think about it, the broadcast tower is now a lightning rod 😆 I wouldn’t doubt those transmitters are system/equipment grounded so that if lightning strikes the tower, most of that energy from the lightning would go straight to the ground and bypass electrical and the FM radio broadcast equipment. Back in 2010 I was in a technical college getting my two years associates degree in industrial electrical / systems technology. the instructor took the students and I on a trip to a 911 Calling Center in Apopka Florida, at that time we were learning, basic communication, electronics and NEC article 250 Which talks about grounding(Earthing )and bonding electrical/electronic equipment. As we walked in inside this 911 Calling Center in Apopka Florida, We walked inside the room where the transmitters were, and we knew some of the equipment had discoloration like some equipment had turned black,next we looked at the electrical panel, the whole electrical panel was blown out. The people at the 911 calling Center was spending hundreds of thousands of dollars installing new equipment because of lightning strikes and power outages come to found out some of the cables to the tower. Weren’t grounded, instead of using copper, it was using aluminum cables. It was using hose clamps off of automobiles to cover the coax cables. It was a mess. The antennas weren’t grounded properly. It was crazy, but it was more of a lesson learned while I was in college, and a very interesting one in communication electronics. there’s probably a lot of reasons why this transmitter is malfunctioning. they might want to call an electrician to check the main power source for voltage spikes and THDFs or transformer, harmonics dating factor on Transformers.
Hi, seems back in the 70’s night time AM radio was full of distant stations I could receive clearly. Now I can hardly hear the same stations, did solid state transmitters make that much difference? Did stations reduce their power? Just wondering.
These days, modern electronic devices introduce a lot of noise and interference. Switched mode power supplies are one of the biggest offenders. So it’s not a matter of transmit power or the type of power amplifier in the transmitter, it’s just that there are a lot of noisy things close to you!
Quick question from someone trying to build a radio, can a SSB signal be heard on a regular radio. Can regular radio be heard on ssb? That transmitter uses only one tube, right? Does that mean its SSB? Or is it doing the full swing. Im assuming you need two valves to get ur full wave and one valve gives u whatever side of the wave u pick, positive or negative, lower or upper sideband, or am I clueless lol
This rig is FM which has lots of sidebands, both upper and lower. AM typically has only 2 sidebands, one on either side of the carrier. When you are talking about Single Sideband, you are talking about eliminating both the carrier and the unwanted duplicate sideband. Single Sideband requires linear amplifiers, but FM does not. In fact, to get the efficiency of an FM transmitter to be high, the amplifier chain is very likely running Class C and quite non-linear. But that non-linearity does not distort the transmitter signal at all. A good place to begin learning more about FM and SSB is The Radio Amateurs Handbook by the American Radio Relay League (ARRL) because both FM and SSB are used by amateur radio operators, and the ARRL Handbooks are very well written.
Those are some of the worst transmitters I have ever worked on. I would rather stick my hand in a QEI or Sparta before that model! But I will say the Nautel and GatesAir units are a work of art!
11Kv anode voltage power output minimum 20KW 🤪😳😳 and filament is 10 volts at 140 amps. Thats not very QRP ... Thats a beast of an amplifier. The power supply must be hudge. If you got a worn tube love to have that. 73s from PD0ROH QTH EINDHOVEN Netherlands.
Consider the cost per hour in terms of consumable tubes and electricity use. If the old stuff was better / less expensive to use, stations would be demanding that they be built.
Maybe for prettiness sure, but for cost to run? Absolutely NOT! It’s still FM and still sounds good. That’s what matters and that’s what the end user is going to hear.
That's a good question - usually we do run into the dummy load, but we were also getting data on how this transmitter performs when actually connected to the antenna so we know what tuning adjustments we need to make. Typically the dummy load doesn't give you that complete picture.
Gosh and tubes are getting harder and harder to find, yes you can get them rebuilt, but those companies are losing business too and soon will probably close shop... then you have a whole lot of equipment not worth anything... and have to switch to solid state. Gotta love technology.. sometimes...
_”Jesus Stick”?_ Is that because if you don’t use it, you might *MEET* Him? Personally? At His place? Or just because you might scream His name when you get zapped? Also, what is in those gas cylinders I saw earlier? Nitrogen or argon, perhaps? And for what purpose? *73 de AF6AS*
Yes and yes. The worst part is, you don’t know which one until it’s too late! The gas bottles have nitrogen in them. We run the gas through a dehydrator and fill our transmission lines with it to keep moisture out and prevent the center conductor from arcing over to the outer shield.
A Broadcast Engineering TH-cam channel. How cool! I was a contract engineer/staff engineer/chief engineer for a little over twenty years with a dozen stations in the southeast. Finally got tired of being on call all the time (even when my name wasn't on the board) so I became an IT geek, and spent the next fifteen years crawling under desks. Retired now, and enjoying Ham radio. Thank you for the memories!
4:08 Please take a look at the Dewalt DCF680 cordless screwdriver. It'll save your wrists from repetitive stress injury, save time, and is about as likely to overtorque or cam out as a manual screwdriver. Not useful for heavy stuff like 2 1/2" wood screws, but great for racks or the rivet nuts on PA cabinets. Gyro controlled, so just a little twist in the direction starts tightening or loosening, more twist goes faster. There's a clutch, but it's unnecessary since you can hold it like a manual screwdriver.
This Broadcast Engineering show is also good for audiophiles who are interested in sound reproduction and broadcasting.
The nice thing about being an amateur is that you can do whatever you want, and not have to do what others demand of you! Enjoy! 😊
Where can I contact you?
Also, remember that your PA tuning will be slightly different between the antenna and the dummy load. Best to tune into the antenna. Dip the plate, peak the grid. On that Harris FM, tune for peak RF TPO. You will notice that the PA tune and load peaks are pretty wide, so skew to the side of the peak that gives lower PA current. That is tuned.
This show touches the heart of radio broadcasting. It is wonderfully excellent.
As a new to the game contract engineer I found this troubleshooting exercise very valuable. Would have really liked to see it go to final fix! Maybe a pt 2?
Many moons ago I maintained a RCA-BTF-20E. It was a pretty good box except for the strip-line tuning- the sliding finger-stock would arc and burn when tuning and the RF-voltage on the 4CX15000 PA plate was very high. A number of them were known to arc and set insulator shelf on fire.
Ours ran as a backup until 2016 when we donated it to a museum. Those were fun when the lamp in the VSWR meter burned out and they'd dump the plate until you figured it out.
Thanks for your reply. I didn't see any covering on the grounding cable. Guess I'll have to look closer next time. Stay safe because those caps do bite. :>)
I enjoyed this. I have an HPX40, currently sidelined until my refurbished tube comes in.
Props to this tx site being so clean!
I don’t think I’ve ever gotten motion sickness from watching a 2D TH-cam vid. But here we are :)
Agreed. A fascinating video spoilt by waving the camera around and giving me eye strain. I gave up after 5 minutes.
I just discovered your channel. I am a TV/radio engineer as well who also started a TH-cam channel. I will have to try something like this when I do an amplifier swap on a Nautel transmitter, which is something I plan on doing very soon.
Most of this is way over my head, but I absolutely love your videos! Please don't stop sharing this kind of thing!
Thank you!! Hopefully if you keep watching nerdy stuff, it becomes not so far over your head!
I was looking at how close the back of that transmitter was to the wall. They're usually installed so there's just enough space to swing the back door open. That causes a major problem; you will have one injury turn into three. If you're in back of the transmitter and touch something that's still slightly energized, you'll burn the tips of your fingers. When you do that, you'll jerk your arm back and slam your elbow into the wall behind you. Immediately after that, you'll pull your arm forward again sharply and slam your nuckles into something inside the transmitter. Thus, one injury turns quickly into three!
Our station engineer told me this story one night when I was in my late teens and working my first job (weekends) in radio. He and I were at the transmitter one night while he was repairing something. We both had a good laugh at it, but in my experiences, it's turned out to be nearly true! That engineer is in his late 80's now and we still laugh about it.
Used to work on commercial AM,FM, and analog TV transmitters. What I see here is very familiar to me. For the past 35 yrs and ongoing work on 250kw and 500 kw SW transmitters for VOA and Radio Marti( they broadcast to Cuba) The site is the only remaining Greenville,NC.plants A site and C site are closed C plant building is used by ECU and is their property(state,county) B plant where I am now is Radio Marti. The hv for the tubes is actually similar to what this commercial transmitter has-but VOA tubes run at much higher current.25A 12kv 250kw 16kv 55A for 500kw. As I typed this “don’t bypass interlocks on transmitters” years ago an engineer was KILLED from the bypass. The tubes used at our plant are water and vapor cooled. In older 250kw GE SW transmitters the RF driver feeding the PA is 50kw. Newer transmitters here have 2 power stages-not 3 as the older GE uses. Also SW transmitters are variable frequency. At the SW plant you tune transmitters several times a shift-each frequency change. This does cause mechanical wear on components. And of course the ground hook is your friend! USE THEM! Filament voltage on one of the VOA tubes is 14v-but over2000A-rectified filament supply! Rectifier diodes mounted on water cooled heatsinks.
Where can I contact you?
Not often I see a 4CX20000, remember thinking my old 4CX250 was beefy ;)
The 4CX250B is the baby of the family. But they work very well in amateur radio amplifiers, typically in push-pull pairs in VHF service. Of course they work well on lower frequencies, too. But if you are interested in doing moon bounce, a pair of those 4CX250s are a good choice.
73 from Bob, WA6WHT ☺️
Aye, when I started in the hobby I bought a set to make my own amplifier, never got it finished though due to.. well... life happened.
Still have them somewhere in the storage.
73 de Soren OZ2AEV
iam happy with my GU74B amplifier on HF bands
As a Radio Amateur operator this video is very interesting. Thanks for sharing. 73 de M3SNU.
Very interesting video.... never thought I'd find this stuff intriguing hut here i am!
I think ur discoloration is just cooked dust. Not that there isn’t an issue but it’s definitely no indication of a bad tube, just that she getting hyot
CPI Data Sheet for the 4CX20,000C shows 13kV as Absolute Maximum for a Class C Amp, grid driven. So, Harris (Gates Air) is just under the Max with 12.7kV on the Factory Test Data sheet but doesn't leave any wiggle room for when the tube starts getting a little weak & needs a little more Plate & Screen Voltage. I have switched to all Nautel transmitters at the sites I maintain.
The 4CX20000 family is rated at a max plate voltage of 10Kv, typical run at 9K. Running them at 14Kv has a high risk of flash over and ruining the tube. I mean
yea what's $10k here or there. You have something wrong with the power supply or regulator circuit in that transmitter which should be fixed before further abusing that tube.
Agree
The factory test data calls for 12.7kV. 14 is still high, but I don't think GatesAir would tell a customer to run this tube at over 10kV if they didn't think it could handle that plate voltage.
13 KV on the plate? That is generating x-rays. Be careful, men. I have an HT-30 (28 KW TPO) that runs 9 KV on the plate and has 81% PA efficiency. You might want to re-tap that HV supply.
Agree 👍
The FTD sheet for this transmitter calls for 12.7 kV/2.95 A on the plate for FM+HD hybrid operation at 21.205 kW TPO.
@@BroadcastBlueprint Interesting! Thank you. Just be advised that you're also generating x-rays with that.
Trust me, broadcast engineers, know that broadcast engineers, get cancer, or at least they used to when they had to tweak the exciter by reaching around the tube in the cabinet
@GWDLABS The copper (they are usually silver plated) fingers are to stop RF leakage. That does not stop x-rays. X-rays are much shorter wavelengths and go through those little cracks. Most of the x-rays are contained within the cabinet when everything is closed up properly. However, there are times when troubleshooting that you have to bypass an interlock or color outside the lines. I've been a broadcast engineer for 39 years and seen it all. Once in the late 90's, I was Chief Engineer of 17 stations all by myself, no help. Now I only have 7 stations.
Nice clean professional installation. Good for you guys! Thanks for the look inside. 🙂 Curious..What's the plate voltage on the RF output tube in the final of that xmit.? Right you just said 13k...LOL nevermind. Tubes run at high voltages whoa! Very different from the modular ones. Power companies love the older stuff, Right? Do you guys keep a spare on hand? Must cost a small fortune.
It sounds like it need to be re tuned the plate and check the loading as well. The VSWR is sending too much power back into the tube causing it to over heat.
Check that bias baybeeee
As I recall, their VSWR was 1.08 to 1. That's not bad. But there are some things to be concerned about there, like that Plate Voltage. It seems a bit high to me. And possibly the cavity tuning may be a bit off, too, so that 4CX20,000C was dissipating a bit more than necessary for the rated power output. There are good ways to observe that with a spectrum analyzer, which curiously I don't recall seeing anywhere in the video. Around transmitters like these, a spectrum analyzer is a very useful tool.
73 from Bob, WA6WHT and transmitter engineer for several San Francisco Bay Area TV stations at various times. 😀
Amazing job
Excellent
Fascinating stuff.
When using the grounding stick, why do you allow your hand to be on the grounding cable. Not good in my book as one day, you just may feel that cap going to ground. Just asking.
Agree I noticed that too I was like WTF is he thinking
The grounding cable on Harris transmitters is covered in a clear cover!
Ever have to use an empty PA tube box as a sit-down toilet?
I am wondering what the filament voltage on the tube you mentioned and are the filaments AC or DC I think you said the tube was 4CX20000. I have just found your channel and the other channel I watch is Geerling engineering which give insight into the Broadcast industry.
For the 4CX20000C tube used in this rig, nominal filament voltage is 10VDC at approximately 140 amps. GatesAir recommends lowering the filament to around 9 volts after about 150 hours of use to keep the tube from going “soft” too quickly. That was never done to this one and so we’ll probably need to replace it soon.
@@BroadcastBlueprint Consider getting a copy of the classic book on the subject, titled "The Care and Feeding of Power Grid Tubes" by Eimac. They explained a lot about filament management to get the longest life and best performance out of vacuum tubes like that 4CX20,000C. I believe it is available as a PDF as well as in hard copy. As I recall, the PDF was free.
I also recommend getting a copy of the data sheet for that 4CX20,000C, so you can see both what the ratings of it are, and also what typical operation as a Class C FM power amplifier looks like
About that exhaust air temperature, it seems a bit high to me, but I am more familiar with the 3XC10,000A7 triode running in low band VHF TV visual amplifier service, which means they were running AB1 or AB2 as grounded grid linear amplifiers. But our exhaust air temperature was around 135 degrees F with inlet air of 65 degrees F, so we had a 70 degree delta between inlet and outlet air temperature. And we checked our air filters with a vacuum gauge calibrated in inches of water. Too much drop across the air filters was the reason to replace them because a plugged up air filter can reduce the air flow through the anode of the tube and the cooling of the socket, as well. Higher temperatures lead to grief sooner. Also when you pull the tube, take a very good look at the contact fingers in the socket. One point of failure is weak fingers that lead to higher resistance contacts with that tube. 140 amps at 10 volts can cause some serious finger heating if they are not all making good contact with the tube base.
Anyway I liked your video, although a chest mounted camera might have shown some of what you were doing a bit better than the helmet mounted camera did.
73 from WA6WHT, transmitter engineer for KTEH-TV54 and KSTS-TV48, San Jose, and KRON-TV4, and KTSF-TV26, San Francisco. I didn't do all of those rigs at once, however.! ☺️
Dry nitrogen to keep moisture out of the feed lines ?
Precisely! Since nitrogen is also a strong dielectric gas, it helps prevent arcing within the transmission line as well.
I knew a few people with 2 of these tubes in a mono banded amplifer.
What are the black gas cylinders for? Are they for keeping moisture out of the coax feeders to the antenna?
Yes! Those are compressed nitrogen cylinders. We connect them to a dehydrator/compressor unit that maintains pressure inside the coaxial transmission line. Nitrogen is a very popular dielectric gas that prevents the center conductor from arcing over to the outer shield and also keeps moisture out of the line.
No Safety Officer ?
It's a good practice to have a Safety Officer who is on scene of any potentially dangerous work.
They observe and tell you if they notice something but also stay out of the danger zone and are there to call for help if someone becomes downed.
They also take readings of RF radiation during the work and log reports for each employee and their radiation exposure.
At NL Industries the Safety Officer kept the logs for each piece of equipment and the total radiation daily and over time for the equipment and each employee.
If an employee was nearing their legal limit of exposure the Safety Officer would put in a request for transfer for the employee so they would not receive any more radiation for the year.
In real bad cases they had people who were given desk jobs or even paid time off.
All the radiation, with very minor exceptions, is non-izoning. The transmitter manufacturer has responsibility for the inherent safety of the device. As far as a safety officer, the chief is there and is hands-on supervising the process.
Bigger than my MX-15 or Crown FM30 😂 that I can only run on a dummy load.
Why have a dummy load and not a tower for it ?
Still running classic Omnia.6
time to upgrade to all solid state transmitters
Thats a lot of copper earthing strip around the place , floors and walls blimmy must cost a fortune to build that room.
As an Electrician, I think one of the reasons why that FM broadcast station has so much grounding is because of NEC article 250. Just think about it, the broadcast tower is now a lightning rod 😆 I wouldn’t doubt those transmitters are system/equipment grounded so that if lightning strikes the tower, most of that energy from the lightning would go straight to the ground and bypass electrical and the FM radio broadcast equipment. Back in 2010 I was in a technical college getting my two years associates degree in industrial electrical / systems technology. the instructor took the students and I on a trip to a 911 Calling Center in Apopka Florida, at that time we were learning, basic communication, electronics and NEC article 250 Which talks about grounding(Earthing )and bonding electrical/electronic equipment. As we walked in inside this 911 Calling Center in Apopka Florida, We walked inside the room where the transmitters were, and we knew some of the equipment had discoloration like some equipment had turned black,next we looked at the electrical panel, the whole electrical panel was blown out. The people at the 911 calling Center was spending hundreds of thousands of dollars installing new equipment because of lightning strikes and power outages come to found out some of the cables to the tower. Weren’t grounded, instead of using copper, it was using aluminum cables. It was using hose clamps off of automobiles to cover the coax cables. It was a mess. The antennas weren’t grounded properly. It was crazy, but it was more of a lesson learned while I was in college, and a very interesting one in communication electronics. there’s probably a lot of reasons why this transmitter is malfunctioning. they might want to call an electrician to check the main power source for voltage spikes and THDFs or transformer, harmonics dating factor on Transformers.
Hi, seems back in the 70’s night time AM radio was full of distant stations I could receive clearly. Now I can hardly hear the same stations, did solid state transmitters make that much difference? Did stations reduce their power? Just wondering.
These days, modern electronic devices introduce a lot of noise and interference. Switched mode power supplies are one of the biggest offenders. So it’s not a matter of transmit power or the type of power amplifier in the transmitter, it’s just that there are a lot of noisy things close to you!
Quick question from someone trying to build a radio, can a SSB signal be heard on a regular radio. Can regular radio be heard on ssb?
That transmitter uses only one tube, right? Does that mean its SSB? Or is it doing the full swing. Im assuming you need two valves to get ur full wave and one valve gives u whatever side of the wave u pick, positive or negative, lower or upper sideband, or am I clueless lol
This rig is FM which has lots of sidebands, both upper and lower. AM typically has only 2 sidebands, one on either side of the carrier. When you are talking about Single Sideband, you are talking about eliminating both the carrier and the unwanted duplicate sideband. Single Sideband requires linear amplifiers, but FM does not. In fact, to get the efficiency of an FM transmitter to be high, the amplifier chain is very likely running Class C and quite non-linear. But that non-linearity does not distort the transmitter signal at all.
A good place to begin learning more about FM and SSB is The Radio Amateurs Handbook by the American Radio Relay League (ARRL) because both FM and SSB are used by amateur radio operators, and the ARRL Handbooks are very well written.
Those are some of the worst transmitters I have ever worked on. I would rather stick my hand in a QEI or Sparta before that model! But I will say the Nautel and GatesAir units are a work of art!
And you used grounding stick with bare hand.......
The stick is non-conductive and the cable has a plastic insulation.
13kv, i would have thought some hv gloves and facemask would be nice
Very cool
11Kv anode voltage power output minimum 20KW 🤪😳😳 and filament is 10 volts at 140 amps. Thats not very QRP ... Thats a beast of an amplifier. The power supply must be hudge. If you got a worn tube love to have that. 73s from PD0ROH QTH EINDHOVEN Netherlands.
0:56 Too much whiz-bang computerized stuff in modern transmitters. Don't you think the simpler, older, pre-computer era ones were better?
Consider the cost per hour in terms of consumable tubes and electricity use. If the old stuff was better / less expensive to use, stations would be demanding that they be built.
The glass tubes were certainly prettier than MOSFETs.
Maybe for prettiness sure, but for cost to run? Absolutely NOT! It’s still FM and still sounds good. That’s what matters and that’s what the end user is going to hear.
Leave it to Harris to put screws where speedclips belong.
Yeah. Interlocks. Disabled would permit 2 transmitters on same antenna against each other... Kkk...
That's an enterprise VPN that computer catches it's IP I presume...
So kool man
I presuma that computer is a part of an intranet network because if it accessible for all may be a little problematic... Kkk...
Why not run the transmitter into a dummy load instead of putting it on air ?
That's a good question - usually we do run into the dummy load, but we were also getting data on how this transmitter performs when actually connected to the antenna so we know what tuning adjustments we need to make. Typically the dummy load doesn't give you that complete picture.
Gosh and tubes are getting harder and harder to find, yes you can get them rebuilt, but those companies are losing business too and soon will probably close shop... then you have a whole lot of equipment not worth anything... and have to switch to solid state. Gotta love technology.. sometimes...
Jerky camera mode?
_”Jesus Stick”?_ Is that because if you don’t use it, you might *MEET* Him? Personally? At His place? Or just because you might scream His name when you get zapped?
Also, what is in those gas cylinders I saw earlier? Nitrogen or argon, perhaps? And for what purpose?
*73 de AF6AS*
Yes and yes. The worst part is, you don’t know which one until it’s too late!
The gas bottles have nitrogen in them. We run the gas through a dehydrator and fill our transmission lines with it to keep moisture out and prevent the center conductor from arcing over to the outer shield.
National Electrical Code violations all over the place. Serious life 😊safety issues
Yep Howard I agree with you
Read my reply
Multiple violations i see