Nice hack! Should mention there are 3 (actually 4) types of ipex connector. I assume we need IPEX MHF1 aka U.FL connector. It's the most popular one. But be careful, they are pretty similar, especially when you can't compare the size.
I'm trying to to a similar design, but with the shielded part of the coax longer. I think the length of the shielded part is very important, maybe as important as the "active" part, based on what I see on my VNA. Maybe since the shielded part of the coax of your design is non-zero, the length of the active part is less than what would be expected from the math, even considering velocity factor and other parameters that could make a shorter length more optimal. I suspect the shielded part of the antenna needs to be 1/4 wavelength (yours is close 0 is a multiple of 1/4). I've been looking for an online resource that discusses design of a linear monopole and includes guideline for length of the shielded part of the coax. Any suggestions for this?
You're right, he doesn't have both sides of the dipole there since he only left a tiny length of shielding. So the RX board is probably acting as one side of the dipole but the impedance may be far from ideal. So I'd make the shield the same length as the unshielded part. But maybe the VNA, or a check of the RSSI, would show it doesn't make very much difference.
Great tip. Would bare part of antenna need to change length (from 21mm) if left some space between connector and end of shielding?. Example if left ~10mm of shielding so have space for mounting and avoiding bare part is not near carbon frame.
THNQK YOU so much because the T antennas are not esay to install on very thight gliders and that was THE point that prevents me to transfer my fleet of 9 gliders from crappy "rf signal weak" frsky to express LRS 2.4ghz
Does the length of the rest of the antenna wire (the still insulated part) matter? For example, if you just do the same at the end, but keep the rest of the coax cable instead of just 2 mm?
It matters. And the longer it gets it matters even more. So, as long as we keep it short it stays a "short line" (opposed to a "long line") and it's impedace can be neglected
Thank you, this is very useful knowledge. Record an episode about ESC soldering. I would like to know if it is better to place the motor cables at the bottom of the ESCs or at the top, as most do. Do you wrap the cables around the standoff or shorter ones directly to the ESC?
Hi Pavel, ....I have a question regarding feeder/collector length for a 915mhz DIY immortal T style antenna. I've made a couple and designed 3d printed centre pieces to reinforce them etc, but it's very difficult to strip the fine active element wires properly and I always end up with a feeder that's too short (shorter than 11cm) due to wire breakage. How critical is the feeder length to the antenna performance? I can't seem to find an answer online to this. and I'm ready to order 15 cm pigtails to make sure I can correct the mistake. Is 5 mm going to make a huge difference in the collector side? I know it's about impedance matching etc. so that's why I ask.
I’ve never done this before but I’m genuinely curious and trying to figure this out. 1/4 wavelength for 2.4ghz is 31.25mm. How is it that you’re getting 20mm as the correct length?
very nice video! I have a couple of antennas lying around that came with frsky receivers. would they also work on the Elrs receiver? how would the range compare to the t-style antenna?
This is exacly what ive done to my HappyModel EP1 receiver last month. I have ipex/ufl coax cable with the same phisical appeareance with the original EP1 antenna. Unfortunately I dont have SWR meter. I already watch your video about antenna. there is velocity factor involved, I did unterstand. So, with my limitation, I came with this aproach. The length of the active part of the original dipole antenna in EP1 receiver is about 54mm . So, then I make length of the monopole active element about 27mm ( I made it half the length of the dipole). Am I at the right spot ? My main concern is I have the same coax cable in terms only on phisical appearance. I did range test, but sorry I cant provide scientific data. I just can say, the range is "good". never failsafe
@ 1:02 - "all you will need is the ruler or the caliper, some kind of pliers to cut the wire, some kind of knife, the pigtail with the IPEX connector, and something to write on the cable" 😁 OK I need an ELRS receiver with an IPEX connector, mostly because I have so many FrSky antenna's laying around doing nothing ..... 😂😎
I've been doing this for my small drones when I only have the UFL version of the elrs rx on hand. I've been using closer to 30mm, so you think 20mm with most of the shield cut down is best after VNA? I'll try this!
What your swr meter shows - is that this antenna is almost useless in the needed range :( I would keep the shield twisting it and making actual dipole or vee style
@@FPVUniversity I agree with you, but any antenna must resonate on its frequency despite its size. 1 means all 100% energy will be transferred by antenna. 2 means 100% loss of the transceived energy :) I will try this as well later today and measure with nanovna. Sometimes the coax is too bad
Hi Pawel, I was wondering if using a 2.4ghz whip antenna like that which comes on the happymodel diamond f4 would work with elrs. Not needing crazy range, just good enough for house and yard flying. Thanks!
Great video! I'm assuming range should be similar to the EP 2 right? Also, Is it possible to create a larger or dual(diversity) antenna for the EP1? Reason I'm asking is that I would like to increase the performance/reception of my 7". The EP1 antenna is pretty small and since we do not have diversity options for the EP1, the drone itself can block the antenna quite a bit when at Range. I'm seeing RSSI DBM of over 105 when flying about 2-3km out which I think is pretty close to failsafe value (I'm using 250 with threshold of 109 dbm i think).
@@FPVUniversity thank you for the quick response. Do you think making a bigger antenna (like crossfire's) is possible and with any benefits compared to the small ep1 antenna?
Is this still safe to do on any of the expresslrs rx's with an additional pa/lna like betafpv nano 2.4ghz and matek diversity 2.4ghz? Could you give the measurement for a similar styled 915mhz antenna and if it is safe to do? Great video. I love these short simple super useful videos.
Cool hack! thank you! Is resistance still 50ohms? does resistance matter for only video transmitter antennas and not passive aerials? perhaps if only the receievr is sending back telemetry
Nice hack! Should mention there are 3 (actually 4) types of ipex connector. I assume we need IPEX MHF1 aka U.FL connector. It's the most popular one. But be careful, they are pretty similar, especially when you can't compare the size.
Made one for my tinywhoop today. Thank you for this tutorial!
glad you liked it
could you test how much range you loose from the original antenna to this self made one, as this is really cool if it's reasonable.
Self made vs ceramic
how much worse is the range vs a T? or is it about the same? why the t?
I'm trying to to a similar design, but with the shielded part of the coax longer. I think the length of the shielded part is very important, maybe as important as the "active" part, based on what I see on my VNA. Maybe since the shielded part of the coax of your design is non-zero, the length of the active part is less than what would be expected from the math, even considering velocity factor and other parameters that could make a shorter length more optimal.
I suspect the shielded part of the antenna needs to be 1/4 wavelength (yours is close 0 is a multiple of 1/4). I've been looking for an online resource that discusses design of a linear monopole and includes guideline for length of the shielded part of the coax. Any suggestions for this?
You're right, he doesn't have both sides of the dipole there since he only left a tiny length of shielding. So the RX board is probably acting as one side of the dipole but the impedance may be far from ideal. So I'd make the shield the same length as the unshielded part. But maybe the VNA, or a check of the RSSI, would show it doesn't make very much difference.
My shop teacher used to tell me that is a scale, the ruler is a leader of a country
Great tip. Would bare part of antenna need to change length (from 21mm) if left some space between connector and end of shielding?. Example if left ~10mm of shielding so have space for mounting and avoiding bare part is not near carbon frame.
Bei dem EP1/2 werden 2 Antennen mitgeliefert. Kann man denn nicht einfach die nehmen die man nicht braucht und daraus seine eigene Antenne machen?
Very useful. 👍
Also +1 for range comparison with EP1 stock antenna and EP2. Just a look at RSSI-dbm versus the others.
I'll check it out
How on earth this comment is 6 days old if the video got released today?...
That is actaully pretty simple :) My Patrons and YT Supporters have an early access
There are 2 Antennas stock in the Packege of the EP Reciever can I modify the antenna whre I have? Then I Not need to Order Nee Antenna from ali
THNQK YOU so much because the T antennas are not esay to install on very thight gliders and that was THE point that prevents me to transfer my fleet of 9 gliders from crappy "rf signal weak" frsky to express LRS 2.4ghz
I broke the ceramic antenna can can I solder on a wire if so in which pad since the ceramic has four pads
if you can figure out which pad is signal wire, then sure, solder to it all the way. Should work
Does the length of the rest of the antenna wire (the still insulated part) matter? For example, if you just do the same at the end, but keep the rest of the coax cable instead of just 2 mm?
It matters. And the longer it gets it matters even more. So, as long as we keep it short it stays a "short line" (opposed to a "long line") and it's impedace can be neglected
Would you be able to check the range of this DIY antenna vs the ceramic antenna?
Thank you, this is very useful knowledge. Record an episode about ESC soldering. I would like to know if it is better to place the motor cables at the bottom of the ESCs or at the top, as most do. Do you wrap the cables around the standoff or shorter ones directly to the ESC?
Hi Pavel, ....I have a question regarding feeder/collector length for a 915mhz DIY immortal T style antenna. I've made a couple and designed 3d printed centre pieces to reinforce them etc, but it's very difficult to strip the fine active element wires properly and I always end up with a feeder that's too short (shorter than 11cm) due to wire breakage. How critical is the feeder length to the antenna performance? I can't seem to find an answer online to this. and I'm ready to order 15 cm pigtails to make sure I can correct the mistake. Is 5 mm going to make a huge difference in the collector side? I know it's about impedance matching etc. so that's why I ask.
Not that much important. I mean it would be perfect to have exact 1/2 wavelengths but a few mm here and there won't affect it that much
I’ve never done this before but I’m genuinely curious and trying to figure this out.
1/4 wavelength for 2.4ghz is 31.25mm. How is it that you’re getting 20mm as the correct length?
You forget about the the fact that electricity does not travel with a speed of light in void. It slows down in a conductor
@@FPVUniversity I didn’t forget, I didn’t know! Haha. Thank you!
very nice video! I have a couple of antennas lying around that came with frsky receivers. would they also work on the Elrs receiver? how would the range compare to the t-style antenna?
This is exacly what ive done to my HappyModel EP1 receiver last month. I have ipex/ufl coax cable with the same phisical appeareance with the original EP1 antenna. Unfortunately I dont have SWR meter. I already watch your video about antenna. there is velocity factor involved, I did unterstand. So, with my limitation, I came with this aproach. The length of the active part of the original dipole antenna in EP1 receiver is about 54mm . So, then I make length of the monopole active element about 27mm ( I made it half the length of the dipole). Am I at the right spot ? My main concern is I have the same coax cable in terms only on phisical appearance. I did range test, but sorry I cant provide scientific data. I just can say, the range is "good". never failsafe
@ 1:02 - "all you will need is the ruler or the caliper, some kind of pliers to cut the wire, some kind of knife, the pigtail with the IPEX connector, and something to write on the cable" 😁
OK I need an ELRS receiver with an IPEX connector, mostly because I have so many FrSky antenna's laying around doing nothing ..... 😂😎
I've been doing this for my small drones when I only have the UFL version of the elrs rx on hand. I've been using closer to 30mm, so you think 20mm with most of the shield cut down is best after VNA? I'll try this!
Yup! This is what my VNA says :)
What your swr meter shows - is that this antenna is almost useless in the needed range :( I would keep the shield twisting it and making actual dipole or vee style
C'mon, it's a small antenna, not an efficient antenna. If you want range, use a properly mounted dipole, not this thing :)
@@FPVUniversity I agree with you, but any antenna must resonate on its frequency despite its size. 1 means all 100% energy will be transferred by antenna. 2 means 100% loss of the transceived energy :) I will try this as well later today and measure with nanovna. Sometimes the coax is too bad
Hi Pawel, I was wondering if using a 2.4ghz whip antenna like that which comes on the happymodel diamond f4 would work with elrs. Not needing crazy range, just good enough for house and yard flying. Thanks!
Any antenna would would as long it's 2.4GHz.
Great video! I'm assuming range should be similar to the EP 2 right? Also, Is it possible to create a larger or dual(diversity) antenna for the EP1? Reason I'm asking is that I would like to increase the performance/reception of my 7". The EP1 antenna is pretty small and since we do not have diversity options for the EP1, the drone itself can block the antenna quite a bit when at Range. I'm seeing RSSI DBM of over 105 when flying about 2-3km out which I think is pretty close to failsafe value (I'm using 250 with threshold of 109 dbm i think).
The range would depend of how good the tune on the new antenna will be. Should be comparable
@@FPVUniversity thank you for the quick response. Do you think making a bigger antenna (like crossfire's) is possible and with any benefits compared to the small ep1 antenna?
Is this still safe to do on any of the expresslrs rx's with an additional pa/lna like betafpv nano 2.4ghz and matek diversity 2.4ghz? Could you give the measurement for a similar styled 915mhz antenna and if it is safe to do? Great video. I love these short simple super useful videos.
Cool. That should also work for the Matek Diversity Receiver, right?
Of course
Hmmm...nice! Will this also work with the 915 Mhz receiver? If so how long would you think the active element should be?
Sure, why not. It should be 55-58mm long but I never tested
Oh, sweet! 😃
Thanks a bunch, Pawel!!!
Stay safe there with your family! 🖖😊
rule 1 of antenna club, never ask about velocity factor....
great video. ❤
Glad you enjoyed it!
Thanks alot
Most welcome
Cool hack! thank you!
Is resistance still 50ohms? does resistance matter for only video transmitter antennas and not passive aerials? perhaps if only the receievr is sending back telemetry
Neither monopole or dipole do not have 50 Ohm impedance. Monopole has 36.5 + j21.25 Ohms
I love it!
We all love small antennas :)
@@FPVUniversity ceramic antenna is polarized?
No, they are linear. They are just shortened monopoles
@@FPVUniversity Want to see that micathane quad in action! noticed them for a while but forgot
Nice 👍🏻
Thank you! Cheers!
Very nice
isn't it?
@@FPVUniversity maybe range test comparison? ;-)