HF newbie questions

[POD]

g'day all, as mentioned in the thread in General Chat, there's obviously a lot of knowledge of HF in the community here, so here's the first of my silly newbie questions;
Radio is a Codan 8525 with remote head, Jenal SC-2 microphone, moonraker auto-tune antenna with Codan controller.
When I make a voice call, the Tx light in the radio does not seem to glow at all. I have done a beacon call with the SC-2 and the tx lamp glowed very brightly, also glows when tuning the antenna so the LED itself is clearly intact. Is the brightness (or lack thereof) of the tx light any indication of transmitting power? Could not make myself heard any further away than about 100km in sked the other night.

[rover-56]

The brightness of the tx led is directly proportional to tx power in a Codan. The radio is clearly transmitting, so it looks like there may be a problem inside the mic, maybe ptt switch, loose connection, or faulty microphone element.
Carbon elements can lose effectiveness if they are old, or have been exposed to moisture. They are easy to replace.

Since you were able to be heard nearby, I would suspect the mic element.

Cheers,
Terry

[POD]

The Jenal SC-2 mic was given to me by DeanoH (thanks Dean!) and wired into the radio by me with guidance from Alan of Jenal communications (can't speak highly enough of how helpful he was, fantastic product support for something he probably sold years ago), the tx light behaves the same way with 2 standard Codan microphones as well, but all 3 mics are probably pretty old.
What exactly is the element, would it be a generic component? Just a matter of a couple of screws and a couple of wires to fit a new one?

[rover-56]

Could be an electret type which is a small cylinder about 1 to 2 cm dia x 1cm long, or a carbon insert type which is much bigger, more like 4 or 5 cm diameter, fairly obvious when you get the handpiece open. Both are generic 2 wire or solder connections, not polarity sensitive.
You just need to get a replacement which physically fits. Jaycar and Oatley and probably RS Components usually stock them.

Terry

[POD]

Will open the mics up tomorrow and make visit to Jaycar, time permitting, they have a branch near my work. Last time I went in there a couple of weeks ago, the bloke who served me was the 8th dwarf, Surly. I'll look for someone else this time!

[rover-56]

Will open the mics up tomorrow and make visit to Jaycar, time permitting, they have a branch near my work. Last time I went in there a couple of weeks ago, the bloke who served me was the 8th dwarf, Surly. I'll look for someone else this time!

Another possibility I just thought of is that Codans have a microphone amplifier inside the main box. If the radio is misbehaving with several microphones it could be that the amp isn't working. It is possible to still be heard faintly without the amplifier, but not have enough microphone power to give full radio output on voice tx.

Bit more complicated to fix but worth keeping in mind.
Lara Electronics are good with Codans.
30 McIntyres Rd, Lara VIC 3212, 0407531588

Terry

[Kevin B]

Could be a much simpler fix than that, first need to know where/how its installed, is it in vehicle or are you bench testing, HF modulation is very susceptible to stray RF where as a CW tone which is generated to tune your antenna is not so much.

[Kevin B]

Could not make myself heard any further away than about 100km in sked the other night.

That is not uncommon in HF operation and could be conditions, there have been many an instance were I have been working a HF band and could not be heard between 500km and 2000km away yet have no prlem being heard 10000km away in the same same sked, 10 mins later it changes, thats HF propogation for ya.

[DeanoH]

Hi POD, from memory (although it was a few years ago) the Jenal mike has a built in (set once) 'volume control' so that it's output level can be correctly set to suit different HF sets. I think this was also mentioned on the Jenal web site, but as I said it was a few years ago.

Hope it woks out OK.

Deano

[Kevin B]

microphone Drive Level

Newer versions of the SC2 and SC3 (PCB Version 3 on) have an adjustable in-built microphone pre-amp. This pre-amp is also fed with a fixed level of selcall signal so that setting the voice level output power to a suitable position should result in an adequate selcall output power level.

Have a look here
Intersting microphone.

http://www.jenal.com/page102.ht