One for the HF and Megapulse experts

Submitted: Wednesday, Mar 30, 2005 at 08:06
ThreadID: 21616 Views:2299 Replies:7 FollowUps:12
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A friend hired a HF radio and found that he could not receive and nobody anywhere (VKS7373 bases included can ever hear him transmit). He found if he disabled his megapulse, he could receive but he still can't transmit. Suspecting a problem with the set, he had it replaced for another, but still had the same problem. I suspect an antenna or cable problem, but had him check with multimeter and all seems OK. He is now at Arkaroola, part way round his trip so limited ability to contact me, but I have advised him via email (which he will pick up some time soon) to put a wire of 8.88 m length directly into the centre conductor of the antenna socket and try that. Also advised him to try battery disconnected from vehicle and HF only connected to battery in case something else is casuing problems like megapulse did.

Any other ideas? Any known issues with HF in 80 series?
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Reply By: signman - Wednesday, Mar 30, 2005 at 08:49

Wednesday, Mar 30, 2005 at 08:49
G'day David,
What radio is he using?? I have a mate with an old 7727 crystal Codan. He gets a loud whistle thru the radio with the megapulse on- but disconnected no probs. receiving or transmitting. I have worked him from Sydney all the way up the Canning. The long wire option definately increases performance- however there is some debate as to the direction it should be sloped. I think the higher end of the wire should be away from the receiving station- giving a better skywave.
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Follow Up By: Member - David 0- Wednesday, Mar 30, 2005 at 08:54

Wednesday, Mar 30, 2005 at 08:54
The radio is a Codan 8525b. Take your comments re antenna wire on board, I used to usde one a faitr bit jammed into the spring coils on the antenna mount.
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Reply By: signman - Wednesday, Mar 30, 2005 at 11:03

Wednesday, Mar 30, 2005 at 11:03
David,
Just had a brainstrorm. Is the Audio Mute turned OFF. With the 8525 the mute is enabled at switch on- and should be switched OFF by pressing the Mute Off pad.
Also, has he got good earth connections. As you are aware the antenna should have a good clean earth- but there is an earth connection on the back of the radio with should have a reasonably heavy wire to a clean chassis connection??
Also, enough grunt in the battery?? I guess you've heard some weak signals on the VKS sessions- but when the users start the engine the signal strength increases dramatically.
But I still agree- the Megapulse WILL affect performance mainly on receive.
If (or when) you resolve the problem I would be interested.
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Follow Up By: Member - David 0- Wednesday, Mar 30, 2005 at 11:12

Wednesday, Mar 30, 2005 at 11:12
signman

He tells me mute is off. You may be correect about earthing because the radio is in a technicians case, and usually the earth from body of radio is just laying in case. Though I would expet that since red and black cables are attached direct to battery, the earth would be OK. I suspect that the radio body earth helps eliminate interference more than anything else, but I could be wrong.

Yeah I sure have heard some weak and garble messages and sent a few too :-)

Will keep in touch

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Reply By: Michael Carey - Wednesday, Mar 30, 2005 at 18:46

Wednesday, Mar 30, 2005 at 18:46
A HF Radio earth is equally as important as the antenna. Generally, a thick wire just isn't good enough (unless it is less than 300mm long). If you are relying on the DC power cable negative for an RF earth, you will be disappointed with the results.
Technically a HF antenna needs a counterpoise, similar to how some UHF antennas need a ground place.
Because RF energy travels along the SURFACE of a conductor, having a thick wire (good for lots of DC current) isn't up to the task of being a good RF ground conductor.
This is why the Codan 9350 autotune comes with a flat earth braid, it is all dependant on surface area!!
When I installed my old tapped whip, I used a 25mm copper strap to connect the antenna base directly to the chassis of my 4x4. This made it work 50% better that relying on the metal to metal connection from the bullbar to the chassis.

For a portable set, I would recommend using several (at least 3) long insulated wires, radiating out along the ground from the ground connection of the radio and/or antenna tuner. For portable use, I would also get a Bushcomm broadband wire antenna. You connect it to the radio, sling it up over a tree and away you go without needing a tuner!

PLUS, one other thing. We are currently at the bottom of the 11 year sunspot cycle. HF conditions are generally crappy at the moment, but they will improve!

Check out www.ips.gov.au for info on HF radio propagation. At the moment, there is a HF radio warning with degraded HF propagaion conditions expected.

Welcome to the world of HF communications!!
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Follow Up By: Michael Carey - Wednesday, Mar 30, 2005 at 19:04

Wednesday, Mar 30, 2005 at 19:04
Should of added this link too :-
http://science.msfc.nasa.gov/ssl/pad/solar/sunspots.htm
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Follow Up By: Member - David 0- Thursday, Mar 31, 2005 at 06:03

Thursday, Mar 31, 2005 at 06:03
The antenna is well earthed on the car bullnar. The set is earthed via the DC cable only. YEs I am aware of current conditions but he can hear me and lots of other stations but can reach none of them all week. I can reach almost all of them.

PS I have been involbed in HF for 20 years :-) but thanks for the welcome ;-)
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Follow Up By: Michael Carey - Thursday, Mar 31, 2005 at 10:34

Thursday, Mar 31, 2005 at 10:34
No Problem,
HF is a tricky thing. I've been a "ham" since 1988 and also work in marine electronics. I've always had an interest in HF radio, especially for 4x4.
Sat phones are great, but there is something about radio... with sat phones (any phones really) there is so much technology that makes the thing work. But with radio, it's you, the person you want to talk to and the ionosphere! You have to tweak things to make it work as well as you can.
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Reply By: Footloose - Wednesday, Mar 30, 2005 at 19:18

Wednesday, Mar 30, 2005 at 19:18
Tell Bruce to make sure that his aerial base is properly earthed to the bullbar or the battery negative. Also the poweroutput can be very roughly determined by watching the red tx led on the set.
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Follow Up By: Member - David 0- Thursday, Mar 31, 2005 at 06:05

Thursday, Mar 31, 2005 at 06:05
How did you know it was Bruce?
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Follow Up By: Footloose - Thursday, Mar 31, 2005 at 06:58

Thursday, Mar 31, 2005 at 06:58
Umm...err....he hired it from me. :))
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Follow Up By: Member - David 0- Thursday, Mar 31, 2005 at 07:22

Thursday, Mar 31, 2005 at 07:22
:-)

Ooops sorry, I didn't mean to drag you out into the open like that.

I have dealt with you before and I must compliment you on your great service. Though Bruce has problems, he has also remarked that you were very helpful. He just didn't have enough time to solve the problems before he set off. Lets hope he gets it sorted.

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Follow Up By: Footloose - Thursday, Mar 31, 2005 at 07:32

Thursday, Mar 31, 2005 at 07:32
No worries, can't stay hidden forever. Only hassles are when I offer advice on some topics that people might think I'm pushing my own barrow, which I take pains not to do. Thanks for the comments, hope it gets sorted out, nothing worse than not being able to use something while travelling.
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Follow Up By: Member Eric - Thursday, Mar 31, 2005 at 07:50

Thursday, Mar 31, 2005 at 07:50
Whats your e-mail footloose , you should keep us informed on what you do . Why should I go elsewere when I can go to a eo member
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Follow Up By: Footloose - Thursday, Mar 31, 2005 at 07:55

Thursday, Mar 31, 2005 at 07:55
Eric, I've been freeloading so far but its time to do my dough I guess :)) I can be reached at jimshire1 at iprimus dot com dot au. Always willing to provide assistance where I can. Making a dollar is secondary but nice (bet you don't believe I said that )
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Reply By: geocacher (djcache) - Thursday, Mar 31, 2005 at 23:13

Thursday, Mar 31, 2005 at 23:13
Three cheers for Footloose. A champion to deal with and ever helpful on the codan yahoo forum.

Can't wait for my new (2nd hand) 9323 to arrive from him, and he's kept me posted as to it's progress every step of the way.

I even actually believe the last bit he said because at his prices he can't be making that much for himself. One of the other better known Codan dealers in Vic's price on the same 9323 and antenna combo at Wandin was exactly $1000 dearer on a good second hand unit. And Footloose patiently put up with my tyre kicking for a few months before I bought mine.

Footloose's web page

And no he didn't ask me to give him a plug. Credit where credits due as far as I'm concerned.

A heartfelt thanks very much Footloose, you can stop blushing now.

For those that are interested the codan forum can be found here and it is full of info. There's possibly a Barrett one too but I've not bothered looking even though they also make good gear, I already owned a Codan when I found it.

Dave

AnswerID: 104612

Reply By: Member - David 0- Saturday, Apr 02, 2005 at 22:24

Saturday, Apr 02, 2005 at 22:24
I heard Bruce log in to Alice Springs today- his first contact with a VKS737 base since he left. I spoke to him at 8.30pm when the scheds had finished. He had a good copy on me but I had a pretty marginal copy until his last over, so I don't know what he has done to solve the problem.

By his reluctance to go to Channel 1, I suspect he is running a wire rather than a multitap, so maybe an antenna, cable or spring base problem. His battery was running down and we had to call it quits but I will listen in for more news.

AnswerID: 104844

Follow Up By: Member - David 0- Sunday, Apr 03, 2005 at 20:27

Sunday, Apr 03, 2005 at 20:27
I spoke to Bruce on the phone today (he is in Coober Pedy). Well it turns out he wasn't reluctant to go to Channel 1, he was in the middle of a huge dust storm and his wife was holding everything down. The wind came from nowhere he said.

Anyhow, it turns out he has done nothing but disable the Megapulse. Still using the multitap. I told him how I had a really poor copy until his last over. He said "Funny you should say that, I noticed the TX light glow really well on the last over." Well I ave never seen my TX light glow much so not sure what the connection is. Anyhow he is getting out to bases occasionally but usually marginal copies. So I suspect everything is not too bad, maybe needs a bit better earth or battery power, but current propogation conditions certainly don't help.

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Reply By: Member - David 0- Saturday, Apr 09, 2005 at 06:24

Saturday, Apr 09, 2005 at 06:24
Hey footloose..just an update....

I have been listening in to the scheds daily and chatted with some of the operators afterwards. We all copy Bruce way way way down low on every single contact.

I threw an old inverted V I had for 8 MHz up into a tree (that took some doing) and managed to get a reasonable contact on him such that some overs were readable. His is definitely consistently the lowest signal on the air, no matter who he is talking to, so he does seem to have a problem, just don't know what it is.

He says all of the electrical and antenna connections check out OK.
AnswerID: 105826

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