How do you test a radio?

cardiffrob · Post by **cardiffrob** » Tue Aug 04, 2009 4:32 pm

I anticipation of one-day needing a radio I have wired in the tray, aerial and cables.
I've got it all working (Valcom 760) and, from inside the nice metal farm building, I can hear Cardiff radar from about 6 miles away. I assume that this is not going to be the most scientific method to test a system so I ask the assembled throng if they could further advise on the best way to prove the system satisfactory for purpose.

I'll attack the paperwork at a later date!

PS Thanks go to John Angiolini for the fantastic aerial assembly, although, soldering a BNC (?) aerial connection is not one of my favourite passtimes. Took the best part of 4 hours to get that sucker done!

Nigel Ramsay · Post by **Nigel Ramsay** » Tue Aug 04, 2009 5:47 pm

Not overly scientific, but... assuming you have a flying pal who could fly near you (?), why not agree a time and use say 129.825 or another frequency from 'tother end of the country and simply make brief tx's as he flies overhead and away from you, with him replying "5's" etc over several agreed distance markers.? Illegal I know but pretty harmless if you keep the traffic to a minimum.

As long as you have 5's at 5 miles (in a FRED?) I reckon you'll be ok!

tnowak · Post by **tnowak** » Wed Aug 05, 2009 8:07 am

I would suggest the following:

1. With engine running on ground, ensure no undue interference from mags/ignition system. Some plug leads/mags aren't screened which will mean the interference is so high you can't hear any transmissions.

2. Choose an airfield with manned radio which is at least 30 NM from your location. Take off and climb overhead your location to, say, 2000 ft and call them, saying it is a radio check transmission. If they hear you 5/5 then your transmitter is fine. If you hear them 5/5 then your receiver is fine.

That checks out your radio for basic functionality.
Tony Nowak

cardiffrob · Post by **cardiffrob** » Wed Aug 05, 2009 10:14 am

Ah. No permit, as yet, so the flying method is out. Isn't there a gadget that tests the output of an aerial?

Nigel Ramsay · Post by **Nigel Ramsay** » Wed Aug 05, 2009 11:32 am

An SWR (Standing Wave Ratio) meter will tell you if your aerial is the correct length, I once had a contract installing radios in military vehicles for Pye (long ago!). Used to install the radio and aerial, then attach the SWR in series and literally clip half an inch off the mast at a time until the meter 'nulled' showing the correct length.

If you didn't already know, an aerial is ideally the same length as the wavelength, or a fraction of it, hence the phrase "1/4 wavelength aerial" etc. That sorts out the efficiency of the aerial. Power, is tested by using a Signal Strength or Watt Meter which shows the transmission strength from the radio... in watts(!).

Actual readability requires an audio test, hence my original suggestion that you organise for someone to fly over you on a nice day and you talk to them!

I just had a quick squizz on EvilBay at " Listed in category: Consumer Electronics > Radio Equipment > Ham Radio > Meters " and there are loads of dual power/swr meters covering our power and frequency bands from as little as a tenner on buy-it-now. As a one-time use purchase, I would guess you could get a reasonably accurate picture of your installation.

tnowak · Post by **tnowak** » Thu Aug 06, 2009 8:13 am

Unless you want to go down the route of VSWR meters (I suspect you don't!), then your testing options at the moment are a bit limited.

I would suggest calling Cardiff for a radio check (push aircraft out of your metal building and phone them first!) to get an idea if they can hear you 5/5 (they should from 6 miles away).

Can you hear ATC at Bristol? That is a bit further away and would be another test of your general installation. Try calling them as well.
Tony Nowak

cardiffrob · Post by **cardiffrob** » Thu Aug 06, 2009 8:56 am

I can hear people in the circuit at Bristol.

I haven't got the PTT wired up yet due to the control column grip being glue on by the previous owner. Smaller than bicycle grips and somewhat similar to the sort of thing on old lawnmower handles. The other problem is that all of my headsets are stereo airliner types ans the headphones only work on the left side and I'm pretty deaf after years of rivetting Seneca nosecones on from within the gear bay! A bit like living inside Ringo Starrs' drumkit.

cardiffrob · Post by **cardiffrob** » Sun Aug 09, 2009 1:58 pm

"Station calling, Carrier wave only" was all I could get out of the transmit when I tried it on cardiff tower. After buggering about for 2 hours I removed the jackplug sockets from their place on the panel and had a look. The lugs that touch the plugs when they are inserted were bent too far back and were not making a connection with the mic supply section of the plug. Problem solved. He got the calsign and gave me "strength 2", which I can live with for an aeroplane inside a metal building at 6 miles.

Does anyone manufacture better quality jackplug sockets?

Job done!

Yippee!
PS Someone gave me 2 pairs of DCH10-40s.

Ian Melville · Post by **Ian Melville** » Sun Aug 09, 2009 3:56 pm

cardiffrob wrote: PS Someone gave me 2 pairs of DCH10-40s.

I thought the FRED was a single seater

cardiffrob · Post by **cardiffrob** » Sun Aug 09, 2009 4:30 pm

He works for HM Gov. They bought pairs of every type of headset to test them out for some specific contract. Obviously, the Bose X won, so......spare sets for everyone. Hooray!

Your tax money at work!

tnowak · Post by **tnowak** » Sun Aug 09, 2009 8:33 pm

Are the jacks you refer to the regular American style? That is, one 1/4" for the headphone and one smaller for the mic? If so, they must have been bent like that for some "purpose". Mine have worked perfectly now for 30 years and no signs whatsoever of wear/bending!
If you want to replace them they are fairly easily available from avionics suppliers and outlets (not Maplin!)
Tony

ColinC · Post by **ColinC** » Sun Aug 09, 2009 9:01 pm

I don't know about 'better' quality but spare are available from http://www.partsforaircraft.co.uk/ specifically here:

http://shop1.actinicexpress.co.uk/shops ... _and_Plugs

Actually I may have some spares myself - will get back to you on that!