UHF and VHF

[Cali]

Does any one use a UHF radio as well as a VHF. I want to use one in my trike and don't want to change my comms if I don't have to. Any ideas?

[ZULU1]

Calli, You obviously wish to use the Australian CB frequencies in the UHF band as well as the normal Aviation band, monitor both frequencies and have a priority transmit feature. The CB radios in Australia and I advise the GME series as they are identical to the Icom F3s, F25, F30 series, these radios are not unlike most PMR radios and are freely available. I am unsure of the intercom system that you have but there are a few issues which make the project extremely difficult to interface. I have good experience with your UHF CB frequencies as well as the Australian brand GME radios. They are very good devices and also reasonably priced in AU$ terms anyway.

I list as it may be easier to understand:

Aviation Band radios and there are really only two left worldwide considering, Icom and Vertex Standard use a four wire confiburation namely :

They do require some form of Microphone amplifier they are AM.

Common (Ground)

PTT (switch to ground to initiate transmit function)

Microphone in and this also supplies the microphone at about 4,7 volts as well as a the AC (voice) the other way, this is the bit that causes concern with the ICOM Ica 6/24 series and has wiped out many people attempting to interface them !

Audio line which is basically the speaker.

PMR radios (Public Mobile Radio) and the type supplied to security guards and so forth..

These radios are very similar to your CB frequencies and are a three wire set up, they are FM and either VHF (which in the case of South America are a special frequency of 144,4 mhz and South Africa at 141,6mhz for low level sport aviation as an example) they live around the PMR and CB frequencies.

The three wire causes confusion and creates havoc to interface them, the best option is to use a relay switching array.

Common (Ground)

Audio

Mic and PTT.

Now this is where it gets interesting, the mic is grounded via the PTT, some old aviation radios worked similar (Icom and Delcom) as well as the Icom ICA110 and its PMR cousin the F110 (we make many sets for Airport Fire tenders in Centaral Africa) but required a dummy load to ground, PMR radios in most cases just switch the mic element to ground. As its FM they have automatic gain control in them. So for example should you be using a Lynx set up, the emmitter follower circuit in the headsets gets hectic and struggles to give full modulation. The system requires no extra parts and a low impedance mic element to connect to ground is ideal. When interfaced with a aviation radio the decoupling capacitors have to be literally bridged out. Also the one radio interferes with the other and vice versa, hence the side tone has to be switched off. I have used both 4016 and 4066 quad switches to do this and finalised on Omron SMD relays as they still bleed through the network. Then when you use a relay you find more aggro as even a diode across the coil does not prevent the back emf flying around the boards.

But I have done it but as yet they are not for sale, Perry in Townsville has a working sample. He has two vee rabbit antennas on the King post of his DTA, one up and one down. The system even went one better with two PTTs on the bar, aviation with the priority and it also has music, instructor override, cell inteface and audio out, trust me not an easy excercise.

Any input I would really be grateful to hear how you get on ?

Ciao Paul (zulu1)

[Cali]

Man you are so far over my head I am not even going to try and answer you

I can give you some more info.
I have an Icom A22 VHF radio
I have an Airmagic Chatterbox coms system.
I have a Uniden Sundowner UHF radio. ( 40 channel ). I would like to use this radio because it has a 5w output over the more common 3w. ( And I already have this one )

For me UHF is far more important than VHF at the moment. I will do radio calls at my private strip and the town strip, but there will be no-one there to hear them. When I start to wander further away I would use it a bit more.
UHF on the other hand will be used a lot. Most of my friends are farmers and they all use UHF. I would like to be able to communicate with them. Range would not be a problem as line of sight would be sufficient, we have 40 channels and everyone uses them. If I have to much range I will transmit to other people on the same channel, that I don't want to talk to.

I have seen systems here where there is a selector switch on the intercom where you can choose between VHF or UHF. Either or, it does not have to be both.
Just an idea on the two PTT's you were talking about. One PTT with two different color buttons would be cool.

I am looking for something very basic. I have spent a LOT of money on Flying related stuff lately and it is getting harder to get clearance from the Minister Of Finance

Cheers

Cali

[Stephan van Tonder]

There are also license issues. Your current aircraft radio license will not actually be legal once you start getting into the UHF frequencies and you would actually have to do a HAM radio course and get a license for that. Yeasu/Vertex have airband radios that can monitor those frequencies but will not allow you to transmit on them.

[Sukkelaar]

Mabe Callie or his father Piet from Ladysmith (Springvale international landingstrip ) might be able to help they use two radios on there trikes, one for normal aircraft use, and the other for the farming community.Which are all on radio for the following (lost cattle,cattle theft, searches, veld fire's and so forth).

Regards
Sukkelaar