Radio problem transmitting only when flying

[horsefeathers]

I'm using a Vertex handheld in a streak shadow, and have no problems with others hearing my transmisions when on the ground, even when taxying. When I'm flying, I can hear others quite well, but it seems others cannot hear me.

 

i'm using a coax feed from the radio to a whip antenna, and the antenna grounded to the metal boom tube (so technically not a good ground plane, i suppose).

 

Anyone have any ideas what the problem might be? I may replace the antenna with a dipole type, but the bottom section of the new antenna would be next to the boom tube, so dont know if that would be satisfactory.Any thoughts?

 

 

[frank marriott]

Try a ground independant antenna [if it isn't already - gererally a loading coil at the base]. Then do a SWR reading [or get someone with a SWR meter to do it]

 

It is only then that you know what power you are actually radiating as opposed to transmitter output into a balanced load i.e. watt meter.

 

 

[cscotthendry]

Are you using an ANR headset? Or does the radio have some kind of ANR feature? The extra engine noise during flight may be causing the radio or the headset mic to block your voice as well. If the ANR or squelch levels are adjustable, you could try experimenting with those.

 

 

[Piet Fil]

Horse feathers,

 

If you're feeling up to a bit of DIY, the following web address may be of use if you want a simple effective antenna to hang off your boom. It describes a simple dipole setup.

 

chrusion.com/BJ7/InvVeeAntenna4ULs.pdf

 

Phil

 

 

[Hongie]

when you are flying and you press your PTT, do you hear the sidetone in your headset?

 

 

[Kyle Communications]

The vertex HH may not have sidetone...if it has it needs to be turned on in settings but that is the best way to tell your mic is working...any other issues will be either RF or antenna

 

 

[Hongie]

The vertex HH may not have sidetone...if it has it needs to be turned on in settings but that is the best way to tell your mic is working...any other issues will be either RF or antenna

ah yes, being a handheld i spose it may not, i didnt think of that.

 

 

[Kyle Communications]

The Icom A6 has the function but you have to turn it on in the settings menu

 

 

[Guest Andys@coffs]

........and have no problems with others hearing my transmisions when on the ground, even when taxying. When I'm flying, I can hear others quite well, but it seems others cannot hear me........

A number of you have jumped to Antenna........If it works on the ground but doesnt work in the air.....what at the Antenna has changed?.........Im guessing nothing and as such it may be a red herring.

 

Unless on the ground means aircraft within 100m and in the air means aircraft Km's away and range is therefore the point of difference.

 

An SWR Meter (specifically covering the VHF air band...so dont use a CB or UHF one unless it clearly covers the airband) is a useful tool at this point just to see what is being Tx'd and what is being lost in reflections back into the transceiver.

 

Also worth having someone else in the air work with you so you can find out if when you transmit they hear nothing at all ie squelch doesnt break so no Rx at all, or squelch breaks but nothing sensible is heard. The 2 are very differnt in fault finding outcomes. The first suggests Antenna/cabling may be an issue the 2nd suggests Tx is Ok but modulation for what ever reason isnt working.

 

BTW I had a 1/4wave whip on a trike mounted on a 90 degree bend attached to some metalwork that held the fibreglass nose pod in place. As a groundplane I expected it to suck really badly....I got 1.1 to 1 out of the SWR meter so practical reality can diverge from theory from time to time. I still dont understand why it was as good as it was, but as is so often the case nobody ever tries in practise to understand why something works when it shouldnt, rather all our energy is put into fixing something that should work but doesnt.....

 

Andy

 

 

[Kyle Communications]

Horse feathers

 

I met you the day your daughter solo'd at gym pie . You need to separate the issues to prove the radio is working fine. If you are coming to Brisbane bring it with you and I will throw it on the Comms test set and make sure it is fine then you have halved the issue. I am 2 minutes from the highway at burpengary bring your headset as well. I will be back Thursday I am doing a the usual getting a pie and coffee at tramcars and will be stopping in at gym pie airport to consume said such food and beverage should be there around 10 am or give me a ring I can have a quick look when I am there if you want

 

 

[Phil Perry]

Does anyone have ANY IDEA how we can "Quieten" the rambunctuous noise on a radio receiver mounted in an SE5A 7/8 scale replica ? It's owned by our Airfield Managing Director, Peter Davis, EX LAA Coach and ex Airline pilot. ( Knows sod all about what makes radios work though ! ! ! ! ! )

 

The aircraft is powered with a genuine Rolls Royce engine, with open plugs ie, not shielded, there doesn't appear to be any legal manner that this can be accomplished on that particular engine. . . . I had metal plug shrouds on my Rotax 503 for years, and never had a problem with engine ignition interference on the receiver, but when these were, for some Godunknown reason made illegal,. . . . no suppressor type cap was able to prevent the level of noise with which I have to put up. I don't mind "Coming off the power" for a short while to receive a clear ATC instruction, but If I asked for a weather report for a proposed alternate destination station by radio, I'd probably be eating treetops if I left it at idle for that long. . . ! ( AND PULEEESE . . . . don't tell me to FLY HIGHER. . . . . It's too darned cold here., the ELR ( European Lapse Rate ) is ten degrees C for every ten feet you go up !! )

 

Phil. ( Amateur Radio Operator G4 OHK - used to be VK4 YC when I lived in God's Country. . . . )

 

 

[Guest Andys@coffs]

The usual fixes are resistive leads, or resistive caps (1 or the other not both) or spark plugs with inbuilt resistor. From memory 582's use BR8ES where the plug without the resistor added is the B8ES.

 

With none of those things you have a great spark gap transmitter

 

If I was in your situation I would want the antenna as far away physically from the engine as I could get and coax with real good shielding. Even then........

 

Andy

 

 

[Phil Perry]

Thanks Andy, yes I've tried all of those things, and you're spot on with the plug types. Being a "Radio Ham" and expected to understand life, the universe and everything. . . . . or so my pilot friends tell me. . . . I've tried all sorts of fixes, until this weekend, when I replaced the plug caps with the old "Illegal" metal cap type, and guess what ?? problem solved. So in future, I will have to carry some resistive ones in my toolkit, so that when I crash again, I can crawl around the back through all the blood and barbed wire, and then change them before the AAIB get there, thereby not invalidating my permit to fly and insurance cover by using unauthorised components. ( ? )

 

By the way, . . . the antenna is mounted atop the Kingpost, as far away from the engine as I can get it short of using one attached to a 100 metre trailing wire jobbie, rather similar to the ones we used to use in the outback for HF comms with Darwin Centre. . . . . ( ! ) And as for the SE5A,. . . . . . I dunno what the heck we can do with that, . . . Peter will know what is legal and what isn't, being plugged in to the UK CAA, but since radio comms were not a problem when that aircraft type was thought up. . . we may well have a problem with LEGAL suppression methods, You wouldn't BELIEVE how long it can take to get a SIMPLE, SENSIBLE AND EFFECTIVE mod thru the various hoops in the UK. . . . . .

 

 

[techie49]

I'm using a Vertex handheld in a streak shadow, and have no problems with others hearing my transmisions when on the ground, even when taxying. When I'm flying, I can hear others quite well, but it seems others cannot hear me.i'm using a coax feed from the radio to a whip antenna, and the antenna grounded to the metal boom tube (so technically not a good ground plane, i suppose).

Anyone have any ideas what the problem might be? I may replace the antenna with a dipole type, but the bottom section of the new antenna would be next to the boom tube, so dont know if that would be satisfactory.Any thoughts?

Hi Horsefeathers,

 

If you solved this one please ignore this reply.

 

If people can hear you on the ground ask them to report on your voice level (modulation).

 

If that's good the problem can really only be the fact your signal in the air is not going where you need it to go.

 

If you're using a quarter-wave whip without a decent ground plane (metal plate or whole fuselage), the signal is probably heading for space instead of horizontally or downwards.

 

As has been suggested by others, a SWR meter at the HH end will give you an idea of the state of feeder and aerial. If the swr is poor (more than 3:1) ratio, your radio may be shutting down the output stage to protect it. This will reduce the signal transmitted. If you don't have a good groundplane, a dipole may be the answer. Again though you need to set it up with a SWR meter to ensure a good match and adjust it to be as clear of metalwork as possible.

 

Paul Toone

 

 

[horsefeathers]

Are you using an ANR headset? Or does the radio have some kind of ANR feature? The extra engine noise during flight may be causing the radio or the headset mic to block your voice as well. If the ANR or squelch levels are adjustable, you could try experimenting with those.

Hi Scott - I AM using an ANR headset, and generally use the ANL feature on the radio as well.I will borrow a different headset, and see if that makes a difference. Also, I'll try the squelch, and also take Hongie and Kyles suggestions about the sideband - maybe the internal microphone is turned on (although i thought i'd checked that when i first set it up...)

 

As I can hear myself whenI transmit, and the red transmit light comes on when I press the PTT (the green light also comes on when receiving a transmission), so i dont think the radio itself is the problem.

 

Kyle, yep, well remember meeting you, your girlfriend AND your wife at Gympie clubhouse the other day. If you're down at Gympie tomorrow, I can see you there. I'll be the one waiting for the crosswind to stop blowing :)

 

 

[horsefeathers]

A number of you have jumped to Antenna........If it works on the ground but doesnt work in the air.....what at the Antenna has changed?.........Im guessing nothing and as such it may be a red herring.Unless on the ground means aircraft within 100m and in the air means aircraft Km's away and range is therefore the point of difference.

 

.....

 

Also worth having someone else in the air work with you so you can find out if when you transmit they hear nothing at all ie squelch doesnt break so no Rx at all, or squelch breaks but nothing sensible is heard. The 2 are very differnt in fault finding outcomes. The first suggests Antenna/cabling may be an issue the 2nd suggests Tx is Ok but modulation for what ever reason isnt working.

 

Andy

Hi Andy,

 

well, your response certainly made me think - as you surmise, the ground transmissions are all very short distance - as you say, probably no more than 500m . I can receive other aircraft from a long way when airborne (heard transmissions from Noosa and the sunshine coast when over Gympie yesterday), so the prob almost cetainly lies in the transmission side - I was flying circuits the other day, and the other planes didnt hear me, or only heard some broken transmissions at the best.

 

When you say modulation may be an issue, what do I check in that regard?

 

Cheers

 

Gerry

 

And thanks for all reponses - radios are just black magic to me...

 

 

[jakej]

how'd the SWR check turn out ?

 

 

[Guest Andys@coffs]

Hi Andy,well, your response certainly made me think - as you surmise, the ground transmissions are all very short distance - as you say, probably no more than 500m . I can receive other aircraft from a long way when airborne (heard transmissions from Noosa and the sunshine coast when over Gympie yesterday), so the prob almost cetainly lies in the transmission side - I was flying circuits the other day, and the other planes didnt hear me, or only heard some broken transmissions at the best.

When you say modulation may be an issue, what do I check in that regard?

 

Cheers

 

Gerry

 

And thanks for all reponses - radios are just black magic to me...

Doesn't make sense to me if it works on the ground up to 500m but not in circuit where aircraft are likely around the same distance then what is the difference (other than height and motion)!

 

Is it that it works on the ground without the engine running, but doesn't work with the engine running. I'd check on the ground engine running and not running.....

 

As to checking modulation, for the purposes of fault finding I gave that info, if the squelch trips on the distant receiver when you transmit but nothing is heard then you have a strong signal being tx'd without modulation (voice payload) if when you Tx squelch doesn't break, or if on the receiving end they turn squelch off but only hear background hiss then you have a Tx/antenna issue.

 

As suggested SWR check in that cassis essential and logically next step. It will tell you what output power you are producing should be >2w as a minimum and if you know the spec for your handheld then at or close to that power. SWR ratio of <3 to 1 and ideally less than 2:1

 

Andy

 

 

[Phil Perry]

Certainly sounds like a weird one doesn't it ??

 

I'd have to agree with Paul and Andy that a vswr check is a good starting point, but PLEASE ensure that the meter is designed for VHF, a CB radio type will not do. Ask around the club and you MIGHT find a friendly radio ham who could well have a Bird thruline wattmeter with a vhf slug available, which you simply reverse in it's socket to read vswr. ( ie, Forward and / or Reflected power ) Vswr is read as a RATIO, and as the lads have already said, a 3 to 1 reading roughly equates to 87 percent forward power, which ain't that bad. . . and unless the radio transmitter itself has it's auto- shutdown protection set quite high to protect it's final transistor or power output module, then this, or a bit less should work.

 

I've never achieved better than one point seven to one ratio with the installation on my flexwing, using a centre- fed, half -wavelength dipole antenna mounted with the centre feed at the top of the kingpost, and this allows good comms for well over 50 / 70 Nm even using the low power setting on the Icom A20 hh. I WOULD get a better vswr reading if I fed the aerial with a balun transformer ( bit of coiled wire and ferrite to match the 50 ohm coax feed impedance to the 70 "Ish" ohms required at the centre of a standard dipole. . . . - but I wouldn't bother going to that depth really as it wouldn't produce a noticeable difference in range. . . ! ) and also NOT have the bottom element strapped PARALLEL to the kingpost, which causes loss into the metal tubing and alo "Skew - Wiffs" the radiation pattern !!!!

 

There are quite a few good aircraft aerials available on the market which are ground independent, should you not have room for a dipole, or insufficient ground plane / counterpoise for a quarter wavelength whip.

 

Anyway, after that burst of Radio "ANORAKS" R us. . . .. you seem to have a slightly different problem, if it works on the deck and not whilst flying. No other ideas , the other guys have suggested the only real alternatives, and that was a really nice offer to have the raadio appliance Health - checked by someone with the gear and the know how. ( fixing problems from several thousand kilometres away is dead easy when you don't have to actually DO IT !! )

 

************ Additional but probably unneccessary info. . . . Should you want to experiment with making your own wire aerials, use 468 divided by the centre frequency you want in Megahertz, this gives a half wavelength Expressed in FEET . . . halve it ( duh ?) for a quarter wavelength. I'll leave it to the Aussies to convert this into FRENCH Kilometres.************

 

Best of luck with your tx problem anyway.

 

Kind regards,

 

Phil

 

 

[horsefeathers]

Thanks to all for your suggestions,but especially to Kyle, who took time out to look at the aircraft. It does seem that the antenna's ground plane (the aircraft boom) is fairly unidirectional, as well as very inefficient. So either a new ground plane, or a ground independent dipole antenna is in the offing.

 

Cheers all

 

 

[dtanner]

Hey Gerry, If I could put in my two bobs worth. I have no problems with transmission or receiving signal, and as we both have the same type suggest you either mount aerial either side of tail boom on metal ground plane under skin, in wing root center section, or at 45* downward facing forward from nose cone allowing enough clearance for turf under nose. I have used both and found works well. I now have a UHF antenna in the under nose position as it seems to work best for UHF as most stations I communicate with are on the ground. With the aerial standing vertical for VHF works well and whether its because it bends in flight or just the ground plane doing it's thing, I'm not sure. Anyway hope this helps. Dave.

 

 

[horsefeathers]

Hi Dave. I bit the bullet, and bought an AirKit ground plane independent antenna a while back - it fixed the problem, and now I have great Rx and Tx performance.

 

 

 

[kermit]

Hi Dave. I bit the bullet, and bought an AirKit ground plane independent antenna a while back - it fixed the problem, and now I have great Rx and Tx performance.[ATTACH]21995[/ATTACH]

Gday cobber, I have a similar problem with my vertex vxa-150 could you let me know where you brought the air kit from and how much , its a real buggar having it there but cant use it properly thanks alot regards kermit

 

 

[horsefeathers]

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