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G/WB-005 tonight and dodgy modulation from the 857

Apologies to anyone trying to hear me on Long Mynd Pole bank tonight, I was informed that the audio was very distorted, no idea why, although it was very windy, and after a day being in ‘shouty mode’ on the telephone to various couriers and other people, I may have neglected to speak rather more quietly :scream:
Checking the menus on the 857 showed no difference from the last few activations and the hint from someone that it “isn’t necessary to have everything turned up to 100” was noted… Although I probably worked that one out a while ago :wink:

As it was getting dark, I gave 23cm a quick go with the new handheld… close to 60 miles with 100mw at both ends was the furthest (of 2) QSOs, I really am impressed with this little rig, I shall wait to see what can be achieved once I get the PCB Yagi wired up, and the longer ‘cheap yagi’ built.

Thanks to the few people who made it into the log, I shall check out the overmodulation on the 857 when I have a few spare minutes!

Don
m0hcu

Hi Don,
What antenna were you using when you got the wrong modulation report?
I ask this question because I had a similar issue once and it was because I was using a long wire antenna and I was operating in a not very ergonomic position in such a way that the microphone extensible cord of my FT-817ND got hooked with the antenna wire, so the bad modulation was due to RF getting into the modulation signal traveling from the microphone to the rig along the microphone cable. As soon as I realised of the problem, and put the microphone cable away from the antenna wire, everything returned to normal.
Good luck on finding the problem.
73 de Guru

Hi Guru,

Ah, very good point… I actually had my linked ground plane antenna on the pole, with 3 radials slanting downwards. Thinking about it, since I was in somewhat of a hurry, being a last minute activation, I was probably sitting a lot closer to the antenna, and ground plane wires, than I normally would be. I also had the rig running 50W rather than the 20-30W I’d normally use, so that could be part of the problem, I do normally get quite good audio reports, but not tonight.
The only other thing I could think of would be the mic. I have a spare one I can try at some point too.

Thanks for the helpful information!

Don
m0hcu

1 Like

Hi Don,
What make / model is the new 23cm handheld? I presume it’s FM?

Ed.

Glad you’re enjoying the Alinco Don!

I am now keen to get a colinear up at home for 2/70/23cm

Speak soon

73

Matt G8XYJ

Hi Don.
I had exactly the same problem with my FT857 on one occasion about a year ago. I had been trying to use SSB on about 7170 kHz with my inverted V dipole and no ATU. The dipole is cut for 7033 kHz and there was quite a bad mismatch. I was told the audio was not only distorted, but it was spreading +/- 10 kHz.

It has not happened again, so I think it was down to the poor antenna matching.

Hi Ed,

It’s an Alinco DJ-G7, very nice little radio, I was looking for one at Blackpool a couple of weeks back, never saw one. I ended up getting it from Nevada who had a nice price for it.

Don
m0hcu

It appeared to be a good match, with just the very bottom of the ‘SWR’ indicator showing
I think that Guru had the right idea, with me being so close to the antenna and radials. I normally use a link dipole, The only other times I’ve a GP antenna I’ve either been further away from the antenna, or used an 817 (with amp sometimes).

I’ll see if I can try it from home sometime, that way I can switch between radios/microphones easily.

Don
m0hcu

Hi Don,
When I had that problem I was running 5 watts out.
In your situation of close vicinity to the GP antenna and running QRO 50 watts, I’m 100% sure the RF was affecting your microphone and causing distorsion to your modulation.

Being too close to the antenna is something we’ll always have to avoid.
I remember when I activated Mt. Bizkai EA2/NV-142 and some hillwalkers arrived to the summit and approched my ground mounted vertical antenna while I was in the middle of the activation sitting on the ground about 12m away of the antenna and I could perfectly feel how the signals received by my FT-817 were attenuated due to the people standing very close to the antenna.
Advise: do never stay or let other stay too close to your antenna.
The endfed antennas installed as a sloper from the top of a sufficiently long fishing pole are very good to avoid these sort of problems. If the lower end can be held elevated about 1,5 or 2m above the ground, that will be just perfect.

Best 73 de Guru

The standard Yaesu microphone has unshielded wires inside a plastic case. And a capacitively coupled RF pickup device (the operator) very close by. It is a low impedance circuit so it is less sensitive than it might be, but it’s not really a good formula for a portable operation nearby the antenna. I don’t know whether anyone has tried spraying a conductive paint around the inside of the microphone case to improve the RF shielding.

The low power of the 817 probably prevents or avoids the problem well enough. But with higher power from a rig intended/marketed as a mobile, it is uncharted territory, though as usual the pioneers have a few injuries.

73 Andrew VK1DA/VK2UH

I’ve had persistent problems (as yet not fully resolved) with homebrewed electret microphone accessories for my 817’s (which I implement following the Raynet “CAIRO” standard). Ones which have worked successfully with several other rigs have suffered badly from RF getting into the audio side. The effectively unshieldable RJ45 connectors don’t seem to be the best choice as a microphone connector and would be glad to hear of anyone else’s experiences/solutions

73 de Paul G4MD

I am reminded of the RF feedback that I used to experience regularly with the FT-857D on 70cm. Careful “screening” of the mic cable using my hand was essential to make my audio intelligible. Can’t say I have ever had an issue with the FT-817ND on any band, even with the BNOS 50 watt 70cm linear in tow.

Hmm, well after being on G/WB-015 this afternoon, and having no reports of any over-modulation, I guess it must have been my vicinity to the antenna a couple of nights ago that was causing the problem.


Operating position on the nice new seat (just a shame someone seems to have tried to set fire to the table :frowning: )

HF Linked GP antenna, and a nice cloudless sky, for a change!

Quite a few QSOs on 20M, and a few on 2m including a ‘normal’ Don (M0HCU/P) to Don (G0RQL) SSB one (the only one on 2m SSB) with the moxon

Thanks everyone for calling in!

Don

m0hcu

3 Likes

Hi Don,
It would be interesting setting up a GP antenna on top of that great tall stone walled tower.
Is it posible to Access to the top of that tower?
Have you ever thought about trying to transmit from there?
Cheers,

Guru

Hi Guru,

It’s only open a few weekend days a year I believe. It was open one day whilst I was there a couple of years ago, and I was going to ask, but they’d locked up and left by the time I’d packed up all my things.
GP antenna may be a little much for there.
I seem to remember someone mentioned on here (Viki M6BWA perhaps?) that she’d been up to the top with a hand held, I could be wrong though!

Don
m0hcu

Hi Don,
Good news that the modulation probleem only appears to have been RF breakthrough from being too close to the antenna.

Like the Moxon (I use them on 6m & 2m from the home QTH) - I guess that’s a really lightweight version to be able to be supported on the fibreglass pole?

Ed.

Hi Ed,

whole thing weights just over 140g (most of that I suspect to be a bnc connector and a straight through bnc connector (Just in case I fancy making a 4m one later) Otherwise it’s all plastic, held together, in a rather bodge-job, with tie wraps :slight_smile:

I can post some photos is you like (here or via emal)

Don

m0hcu

Hi Don

Yes I did get permission from the volunteer ‘guardians’ to go up Flounders Folly and use my VX7 radio but I didn’t have much time and it is pretty cramped up at the top. I leant over the battlements and using the long stick aerial on the handy finally managed a contact with someone living near Cannock Chase and had no time to try any longer. It would inconvenience other visitors if you tried to put up anything other than a handheld mast (eg clutching a 2m dipole) so I wouldn’t recommend it. There is also a super view from up there - certainly worth a climb up the steps even if you don’t take your radio.

Opening times are normally the last Sunday in the month with some extra at Bank Holidays and heritage open days. The tower is visible from the A49 and the tower is open if the flag is flying! Details on http://www.floundersfolly.org.uk.

73 Viki M6BWA

Hi Don,

Crikey only 140g, that’s impressive.

I think it would be of interest to activators if you don’t mind posting a few photos - I’d suggest as a new thread in the equipment / antennas section would be better than in this thread.

Ed.

Hi Ed,

No problem, I’ll sort some pics out in the next couple of days and put them there.

Don