The AF gen output can be used to check signal to noise ratio. Knock together a BNC to radio MIC lead. Put the test set into TX Test. Put the radio into TX. The radio will get the above signal at the MIC socket and transmit it to the test set. Because the test set know the frequency and amplitude of the tone it generated, it can measure and display the resultant S/N ratio. Any decent radio manufacturer will state the signal to noise ratio that the radio can achieve for a given input. For the lead, I usually butcher a cheap speaker microphone by cutting off the microphone end and terminating in a DIN plug. Separately, I have a small project box with a DIN socket which accepts all my leads, along with two BNC leads, one for AF in and one for AF out (to go to the test set). The box also has a momentary push switch for PTT along with a toggle for longer tests.
Great video, I've got a Motorola R2001D (R2010D) here which is playing up, I noticed it intermittently goes off frequency by a few 100hz randomly, it's not the 10MHz reference as I've tested that and also fed in a 10MHz and it still does it. I recapped the PSU's and the CRT boards, re-seated cards and cleaned contacts. But cannot locate the fault. I have a feeling it's the A9 card and I don't have a PCB extension here for the cards so cannot fault find it. So I'm off to buy a Marconi 2955R tomorrow. But I did not realise it does not do SSB! So now I'm not sure what to buy. I'm in the UK and R2001's are extremely rare.
I used to use these for Her Majesty 20+ years ago. You get a lot in a small package. The IEE488 (GPIB) general purpose interface bus allowed most of the functions/inputs/outputs to be controlled auotmatically from a PC. Using a GPIB switching system lots of pieces of test equipment could be linked and switched automaically, signals conrtolled and measurments recorded and even pass/fail reports printed out. However the rise of USB has rendered GPIB obsolete.
Hi Brenton, interesting comment regarding RF techs having female children. I'm a power linesman working 132kV and over 35 years I've noticed the same in my colleagues!
Hi i use a mixer so i can listen to SSB on the 2955, and input the 2955 signal generator to the mixer And then the lo out of the mixer to the AF input of the 2955, So you are re inserting the carrier using the mixer and the 2955 Dave Browne 2E0DMB
I love your videos! have the 2955B and use it daily. Favorite functions are for quick transmit testing for power-frequency, and receiver testing for sinad and s/n ratio. Works great for old CB's to find which crystals are bad and if the receiver is to spec. When restoring old radios its great for the quick once over to see if the unit is in or out of spec! Maybe do a video with that Lafayette HB600 to measure each channel crystal for frequency and check receiver performance for sinad and s/n ratio to see how close it to .5uv! I have an HB600 I restored and it performs at the .5uv on receive at 12 db sinad and 10db s/n according to the 2955B. Cheers Don
Only problem i noticed with this unit is the exposed bypass switch relays that controls the input from the connector to the option receiver or to the main unit. The relays are exposed and subjet to get moisture and dirt thus one day they might get stuck when change from receiver to tx mode...
Yours is in nice condition. I love my 2955B its much better than the 2955 and 2955A. The only letdown is the lack of ssb measurement. I use mine for vhf and uhf measurement mostly.
G day from Japan. Your Marconi `s power shows watt and dBm. But my 2955B software version 03 only show watt. I wonder why... What is your version? Regards 73s
That Marconi is a very nice unit. Now I have to find one for myself because my test set was made for working only on CB radios. My 8 watt Baofeng UV-82HP does only 5.7 watts on high on 2 meters. On 70cm is is barely over 4 watts. So much false advertising with these Chinese radios and they have terrible harmonics. I regret getting it since I could have purchased a Yaesu FT-60 for not much more. Lesson learned!
Measuring a spectrally bad radio is easier if you don't use auto tune on the 2955B but instead define the expected frequency, it will then read frequency error and the acquire time is even faster. Not all of the Chinese rigs perform like this one, the most hated one is an order of magnitude better.
You made some comments about scientific licenses in the description if I’m not mistaken that radio can be used on the ham band do you have a standard or above class license because of the out
The AF gen output can be used to check signal to noise ratio.
Knock together a BNC to radio MIC lead.
Put the test set into TX Test.
Put the radio into TX.
The radio will get the above signal at the MIC socket and transmit it to the test set.
Because the test set know the frequency and amplitude of the tone it generated, it can measure and display the resultant S/N ratio.
Any decent radio manufacturer will state the signal to noise ratio that the radio can achieve for a given input.
For the lead, I usually butcher a cheap speaker microphone by cutting off the microphone end and terminating in a DIN plug. Separately, I have a small project box with a DIN socket which accepts all my leads, along with two BNC leads, one for AF in and one for AF out (to go to the test set). The box also has a momentary push switch for PTT along with a toggle for longer tests.
Great video, I've got a Motorola R2001D (R2010D) here which is playing up, I noticed it intermittently goes off frequency by a few 100hz randomly, it's not the 10MHz reference as I've tested that and also fed in a 10MHz and it still does it. I recapped the PSU's and the CRT boards, re-seated cards and cleaned contacts. But cannot locate the fault. I have a feeling it's the A9 card and I don't have a PCB extension here for the cards so cannot fault find it. So I'm off to buy a Marconi 2955R tomorrow. But I did not realise it does not do SSB! So now I'm not sure what to buy. I'm in the UK and R2001's are extremely rare.
That radio is very interesting!
I used to use these for Her Majesty 20+ years ago. You get a lot in a small package. The IEE488 (GPIB) general purpose interface bus allowed most of the functions/inputs/outputs to be controlled auotmatically from a PC. Using a GPIB switching system lots of pieces of test equipment could be linked and switched automaically, signals conrtolled and measurments recorded and even pass/fail reports printed out. However the rise of USB has rendered GPIB obsolete.
The selling point when they were introduced was the ability to capture a transmitters ‘signature’ thus allowing forensic proof of wrongdoing.
Hi Brenton, interesting comment regarding RF techs having female children. I'm a power linesman working 132kV and over 35 years I've noticed the same in my colleagues!
Hi i use a mixer so i can listen to SSB on the 2955, and input the 2955 signal generator to the mixer
And then the lo out of the mixer to the AF input of the 2955,
So you are re inserting the carrier using the mixer and the 2955
Dave Browne 2E0DMB
I love your videos! have the 2955B and use it daily. Favorite functions are for quick transmit testing for power-frequency, and receiver testing for sinad and s/n ratio. Works great for old CB's to find which crystals are bad and if the receiver is to spec. When restoring old radios its great for the quick once over to see if the unit is in or out of spec! Maybe do a video with that Lafayette HB600 to measure each channel crystal for frequency and check receiver performance for sinad and s/n ratio to see how close it to .5uv! I have an HB600 I restored and it performs at the .5uv on receive at 12 db sinad and 10db s/n according to the 2955B. Cheers Don
I would’ve checked/changed the lead before doing the video 🤔😂
Hope you’ve fixed it
Only problem i noticed with this unit is the exposed bypass switch relays that controls the input from the connector to the option receiver or to the main unit. The relays are exposed and subjet to get moisture and dirt thus one day they might get stuck when change from receiver to tx mode...
As a complete amateur I have so many questions. I do physical radio repair but need so much advice on how to properly use this device.
Yours is in nice condition. I love my 2955B its much better than the 2955 and 2955A. The only letdown is the lack of ssb measurement. I use mine for vhf and uhf measurement mostly.
Do you know the standard data(EMF Level) for motorola GP3188?
G day from Japan. Your Marconi `s power shows watt and dBm. But my 2955B software version 03 only show watt. I wonder why... What is your version? Regards 73s
Good information... subscribed 73.
That Marconi is a very nice unit. Now I have to find one for myself because my test set was made for working only on CB radios.
My 8 watt Baofeng UV-82HP does only 5.7 watts on high on 2 meters. On 70cm is is barely over 4 watts. So much false advertising with these Chinese radios and they have terrible harmonics. I regret getting it since I could have purchased a Yaesu FT-60 for not much more. Lesson learned!
Are these hard to find?
Maybe it need to be plugged in to a different power source? The radio, to put out full power!
Measuring a spectrally bad radio is easier if you don't use auto tune on the 2955B but instead define the expected frequency, it will then read frequency error and the acquire time is even faster. Not all of the Chinese rigs perform like this one, the most hated one is an order of magnitude better.
.8uV to break squelch?! That's pretty bad.
A modern Motorola DMR handset will break squelch at .2uV
You made some comments about scientific licenses in the description if I’m not mistaken that radio can be used on the ham band do you have a standard or above class license because of the out
18w out of a handheld? Yikes.