Dual Radios

[Keith W]

Im fitting another radio radio to my Jabi, both are Becker 4201, do I have to fit another antenna or can I buy a splitter and just run the original antenna, thanks Keith.

 

 

[Rastus]

G,day Keith,

 

I think you would be best served with a second antenna, well separated from the existing one. Most, if not all, GA aeroplanes have one for each radio. The opportunity for transmit energy to fry the receiver of the second radio is too great a risk. The Piper Archer I was flying today certainly has two Comms antennas widely spaced on top of the fuselage.

 

I speak as an Amateur radio operator licenced for more than 30 years.

 

Mark Kyle will be well qualified to give an opinion as well. He has more years experience in the communications industry as a supplier and repairer of various commercial and amateur transceivers than he would care to count.

 

Robert

 

 

[derekliston]

Im fitting another radio radio to my Jabi, both are Becker 4201, do I have to fit another antenna or can I buy a splitter and just run the original antenna, thanks Keith.

I have two radios in my CH701. I use two antennae one on each side of the fuselage above the baggage area and just behind the skylight. Works well.

 

 

[Ayecapt]

2 aerials as others have stated . Make sure you correctly cross interlock the two radios. The installation manuals will show you the correct terminls to connect to the other radios PTT . If you dont do this you risk getting very severe and annoying noises from the non transmitting radio. . Due to the tramsmitting radio signal forcing its way through the front end of the receiver on the non tx radio, even if it's tuned to another channel . ( front end overload defeats the recievers selectivity )

 

 

[jetboy]

2 aerials and minimum spacing quoted is normally 4 ft or 1.3m also applies to spacing from any other similar frequency antenna such as ELT

 

I dont quite meet that requirement on my 701 have chosen to use the aft corners of the roof plus one at the central rear of the extended baggage bin

 

you would normally use separate ptt buttons for each VHF or a transmitter selector switch on the panel (such as a Cessna or PS avionics type audio panel has)

 

I have never cross - linked transmitters or audio you could dig up the wiring scheme for a common GA twin VHF installation to see if its done. Becker should have the info a lot of their radios are dual installations

 

 

[Ayecapt]

Couple of screen shots for a Garmin 250 series att . Look at Pin 12 and note 3.

 

As i said you can run into trouble with front end overload. So if the radios have the cross link feature you should use it as well as correct aerial separation. Cross linking is easy enough if you use a mic / ptt changeover switch.

 

Thats about all on this from me.

 

 

 

 

[derekliston]

Couple of screen shots for a Garmin 250 series att . Look at Pin 12 and note 3.As i said you can run into trouble with front end overload. So if the radios have the cross link feature you should use it as well as correct aerial separation. Cross linking is easy enough if you use a mic / ptt changeover switch.

Thats about all on this from me.

I don't have cross linked transmitters nor are my aerials 1metre apart, probably about 900mm and I have a transmit select switch so I can monitor both radios and transmit on either. Touch wood as they say, it all works well. Problem I do have though, is if I am flying two up and we are both wearing ANR headsets I get a lot of noise in the phones at full power run up on the ground. Goes away at anything less than full rpm so no problem for taxi calls, enter and line up, rolling, downwind or anything else. Not there with single headset so it puzzles me.

 

 

[Kyle Communications]

Derek if both headsets are not the same this can cause weird crap to happen on a lot of the intercoms. Its all got to do with mic and speaker impedances.

 

Two radios are fine provided you can get enough antenna separation. Distance is your friend. Most airband radios are around 5 to 7 watts so its not a big RF field to be snotting the RX in the other radio but I have seen it happen on plenty of UHF CB dual radio installs especially in big machinery or trucks where the front end on one of the radio dies.

 

I would put one antenna on the top of the aircraft and the other underneath if you can fit it. If not then one over the cabin or wing and the other down the back near the fin. This way you have as much separation as physically possible and that is what you have to live with.

 

Mark

 

 

[Kyle Communications]

Hey Rastus are you in the blue and white Piper that often does orbits over Fountain road at Burpengary ?. ..same as me doing orbits over my place on the way back to Ycab

 

 

[Keith W]

Thanks everybody my harness is the same as Derek's , just need to work out the antenna, Keith.

 

 

[derekliston]

Derek if both headsets are not the same this can cause weird crap to happen on a lot of the intercoms. Its all got to do with mic and speaker impedances.Two radios are fine provided you can get enough antenna separation. Distance is your friend. Most airband radios are around 5 to 7 watts so its not a big RF field to be snotting the RX in the other radio but I have seen it happen on plenty of UHF CB dual radio installs especially in big machinery or trucks where the front end on one of the radio dies.

 

I would put one antenna on the top of the aircraft and the other underneath if you can fit it. If not then one over the cabin or wing and the other down the back near the fin. This way you have as much separation as physically possible and that is what you have to live with.

 

Mark

As I said Mark, radios work fine, no problem, only with two headsets plugged in. Both headsets are identical ANR types bought from this site and as I said noise only happens when I do a ground power check. I can live with it, I just don't know the cause, almost sounds like amplified feedback.

 

 

[Rastus]

Hey Rastus are you in the blue and white Piper that often does orbits over Fountain road at Burpengary ?. ..same as me doing orbits over my place on the way back to Ycab

G'day Mark,

 

Nope. The green and white one that lives in the end hanger just across from you near the new clubhouse. She doesn't come out as often as she should. That must change. We just had to overhaul the engine because of internal corrosion caused by lack of regular use. Lumps of metal half as big as grains of rice in the oil filter.

 

A lesson well learned, and &$/@/; expensive.

 

Luckily, we dodged the Lycoming AD re. sub-standard con-rod bushings when it was rebuilt.

 

Robert

 

 

[derekliston]

 

As I said Mark, radios work fine, no problem, only with two headsets plugged in. Both headsets are identical ANR types bought from this site and as I said noise only happens when I do a ground power check. I can live with it, I just don't know the cause, almost sounds like amplified feedback.

Just a couple of pics. Radio antennae on each side and Skyview GPS antenna in the middle and further back and then panel with Skyview and dual radios.

 

 

[Toestub]

Derekliston, I just realised your the owner of the plane mine is tucked behind, hopefully get to say gday at Massey if I ever see you at the blue hanger.

 

 

[derekliston]

Derekliston, I just realised your the owner of the plane mine is tucked behind, hopefully get to say gday at Massey if I ever see you at the blue hanger.

Good to hear from you. As I've said previously, because I am retired I can fly weekdays and I usually fly early for hopefully smoother air. I avoid weekends a bit but I'll be there for Wings over Warwick on the 9th. I'll be wearing a Zenith STOL tee shirt. Trouble is I might be wearing a coat over it if past years are anything to go by! Might see you there.

 

 

[derekliston]

Good to hear from you. As I've said previously, because I am retired I can fly weekdays and I usually fly early for hopefully smoother air. I avoid weekends a bit but I'll be there for Wings over Warwick on the 9th. I'll be wearing a Zenith STOL tee shirt. Trouble is I might be wearing a coat over it if past years are anything to go by! Might see you there.

By the way, where is Silverwood?

 

 

[Toestub]

Connolly dam area.

 

Definitely will be at wings too, will keep eye out for you

 

 

[Keith W]

Hi all I'm chasing the backshell connecter that fits on the back of the Becker radio the harness plug locks onto this, I'm not sure if it's a Becker part or a general electrical part,if any one can tell me where to get one or what parts to buy thanks Keith.

 

 

[Kyle Communications]

I think its just a std DB15 connector..you cant usually buy shells by themselves. But they are pretty cheap anyway

 

jaycar has them

 

 

[Keith W]

 

 

 

[Kyle Communications]

You have the backshell there...there should be a set of screws for the backshell

 

 

[jetboy]

looks like the radio doesnt have the threaded receptacles

 

you can buy these from places like Jaycar or get from a computer etc.

 

they are like threaded studs - need to get the correct threads

 

check the radio manual make sure removing the screws is OK they may have other means of securing the plug

 

 

[ruffasguts]

[ATTACH=full]51871[/ATTACH] [ATTACH=full]51872[/ATTACH] I think I'm missing a bracket or clip of the back of the radio that the plug shell secures to

These radios have a slide clip which moves sideways latching I the grooves in the 2 screws I may have one in the hanger will look tomorow

Mick W