Comm Receive and Transmit Issue

[robcaldwell]

Thanks to everyone for all of the suggestion and help! I moved the antenna further up the tunnel (forward) similar to what whee and Battson have done on their birds. I am receiving and transmitting perfectly now! Even in the hangar, with the door closed, I can receive the AWOS when previously I could not pick up the signal when parked directly in front of the transmitter...

This move required rerouting the VHF RG400 coax cable. When doing this I discovered that I had originally routed the cable beside one of the GPS coax cables. I read somewhere that VHF and GPS cables should be as far away from each other as possible. Possibly separating them was the culprit? I also believe that I now have a much better ground plane, as well as improved line of sight with the antenna more forward and up and away from the gear legs. All of these issues I think contributed to the radio performance. All is good now!

(Now, I just need to figure why I have no ADS-B OUT. I am working with Aerotronics on that issue today...)

[gregc]

Rob,

Congratulations for getting is working - that's what counts! Also, I am wrong a lot and might well be again , but just for discussion purposes:

- Looking at your original picture, you had plenty of aluminum for a ground plane. Optimal size is 1/4 wavelenght (+/- 24 inches at 122Mhz). My last aircraft antenna was short, bent, and on a 4" wide fairing and it worked fine. My 2M ham antenna is just sitting on top of a steam radiator in the house and it easily keys a repeater 10 miles away. It's just not that sensitive/critical.

- I also doubt the there was much effect from having the radio coax near the gps coax. In general the reason for not doing so is that, when transmitting, you don't want to couple RF into the GPS, not that the GPS affects the radio.

- Finally, is your hangar door metal? If you can receive the AWOS through a metal door now, how could having the fuselage in the way before make that big a difference?

I still suspect an intermittent connection at one of the coax fittings.

Greg

[jcowgar]

Rob,
I still suspect an intermittent connection at one of the coax fittings.

This is the only explanation that makes sense. I would double check your coax fittings to make sure you don't have a problem going forward.

[Nev]

Am I likely to require a doubler in this location? (It’s not the aerial I was planning on)

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[Battson]

I would go for a doubler.

[500AGL]

Unless that skin is a lot thicker than expect, I will say yes.
Also, assuming that’s your OAT probe I see next to the exhaust pipe, you will need to move that a long ways.

pb

[Battson]

Uhh.... I think that's a cleco?

[500AGL]

Hah!!! You’re right. Don’t drive and look quick at photos. Lol. 🤦‍♂️

[Nev]

Thanks gents. I’ll add a doubler.

Incidentally I’m going to change to a Rami AV-17 Comm antenna. Reason is that I can then easily disconnect the cable inside to remove the panel for maintenance. I didn’t realise that this one had a fixed cable. Both the Transponder and ADSB aerial are easily disconnected to remove the panels entirely.

[Nev]

Actually I’m going to order the Rami aerial shown below, which comes with a “backup plate”. Has anyone used this model and if so I’d be interested to know if you used a doubler, or how it was mounted. Thanks.

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[robcaldwell]

I'm using the Comant CI-122. Also used a .063 doubler in the tunnel fully forward. Great antenna. Got a "Loud and Clear" from a FBO 90 miles away.

https://www.aircraftspruce.com/catalog/avpages/comant122.php

[Nev]

robcaldwell What material did you make your doubler from Rob ? My tunnel is stainless, wondering if the doubler can be aluminium.

[robcaldwell]

I installed 6061 T3 AL to the inside of the SS tunnel. .063 thick.

[N3UW]

Thanks gents. I’ll add a doubler.

Incidentally I’m going to change to a Rami AV-17 Comm antenna. Reason is that I can then easily disconnect the cable inside to remove the panel for maintenance. I didn’t realise that this one had a fixed cable. Both the Transponder and ADSB aerial are easily disconnected to remove the panels entirely.

Nev. to save the money of replace if the antenna you could add a BNC male and a BNC female to give you the same results at a cost of only a few dollars.

[Nev]

I added a doubler this morning, connected everything up then wheeled the plane outside for a real world test.
Christchurch airport is 10nm from my house. I’m getting the ATIS and tower etc very well ……loud and clear.

However when I transmitted for a radio check they replied “carrier wave only”.

I also noticed immediately that when I transmit, I can’t hear my own voice through the headset (side tone). On all radios I’ve used, I could always hear sidetone through the headset when I transmit.

Could the two be related ? Any ideas ? The radio is a Dynon brand (Trig VHF I believe) with a Dynon radio head.

[Mark Dickens]

I assume you have more than one headset jack installed? If you haven't tried the other one, do that and see what happens. The reason you're not getting sidetone (where you hear your voice through the headset) is that your mic output isn't properly wired into the radio. Sidetone comes from the radio back into the intercom/audio panel, so if your voice isn't making it into the radio, you won't get sidetone. Your headset jacks could be miswired, or your mic connection into the radio might be miswired or broken somehow

[Nev]

Mark, thanks. I had the transmit buttons paired with the offside microphone. Problem solved.

[Luke68]

Rob
I noticed in the picture on page 1 that you have what I assume is your transponder antenna on one side and your ADSB on the other side of the tunnel with the comm in the middle. Now that you’re flying is this setup working out or would you change it?
thanks
Luke

[triumphantduke]

^ bump robcaldwell , I'm also curious about this side by side setup -- keeps space available incase a belly pod ever becomes desired

[robcaldwell]

^ bump robcaldwell , I'm also curious about this side by side setup -- keeps space available incase a belly pod ever becomes desired

Sorry guys missed this... I have not had any trouble with either of those two antenna locations. ATC sees me and my position quite well.