The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Animal

The best antenna is one that is resonant on the frequency you want to TX/RX on and that suits your requirements (mobile, base, directional, compact, etc etc etc ?)

Animal

Bit late with the reply :oops: but I found some pics of a four element quad mid build and some of the four element loop driven yagi hoisted aloft! http://i1117.photobucket.com/albums/k593/swoodcock1/Quad3_zps0e55f344.jpg http://i1117.photobucket.com/albums/k593/swoodcock1/IMG00028_zps8a13b8da.jpg ht...

Animal

Great job HomerBB

I had an Avanti Sigma IV back in the day (circa 1980) & worked the world on 12w ssb

Last home-brew for me was a four-element loop driven array - I'll post some pictures when I get time.

Keep up the good work

Animal

Hammer sorted - just need the anvil!

Did you ever manage to perfect that mod for 5kc steps on the Grant by the way - seemed like much better idea than fiddling around with the clarifier & a frequency counter to get the zero's

Animal

Quite correct Dave - glad you're paying attention at the back! =D> You'll find that the extra inductance will also give you more downward shift than up & you'll need to reset the VCO offsets (& probably find that you can't align it correctly with the Coarse control in the center notch positi...

Animal

This reply is obviously a bit late but may help someone else.

Try adding a 5.6uH coil in series to 0v end of the varactor diodes

Animal

Thanks for the additional info Norm It's working very well but I can hear a very slight buzz (which stops when I touch the mic plug) on another receiver :| The other thing I noticed is a trimmer inside the mic (not the gain control which can be adjusted via a hole in the back of the mic) Anyone shed...

Animal

No Dave,

Checked the voltages & all seemed to be in order.

I've ordered some of those large cap varicap diodes (25-500pF) & will let you know how I get on.

Steve

Animal

It's the black front version Dave (with both coarse & fine) but the coarse only moves 2kc either way.

Animal

Cheers Dave

I tried it last night without the mod & the charge from the capacitor died after about five seconds!

CQ DX CQ DX CQ DX CQ DX .....................

Animal

zodiac wrote:Steve,
D44 is for Mid and Hi bands, you have unlocked the clarifier haven't you ?.
Dave.

I didn't realize it needed unlocking tbh Dave

How do I do that exactly (I have my claw-hammer & oxy-acetylene torch at the ready!)

Cheers

Steve

Animal

That's because they are, I said D1 is on the crystal board, I didn't say D4 was as well. Dave. That's me on the naughty step (again!) :oops: Okay, swapped D1 from the Xtal board on the Concorde into the Grant (D44 position) & it's just the same (all three bands) I know that one diode is used fo...

Animal

I've just got a K40 compression microphone & was thinking of wiring it up to the Cobra 148 GTL-DX Will the voltage of the switching line (approx. 3.6v on my Cobra) be enough to charge the capacitor inside the mic? I seem to remember some sort of 'power conversion' kit being supplied with the ori...

Animal

Dave,

On the Xtal board of the Concorde 2, D1 & D4 look totally different to each other?

Steve

Animal

That's normal Steve, you have to change both the varactor diodes D40 and D44 one for each crystal to get it to shift further for the same as what's in the Cobra 148GTL DX MK2 MV201, have you got a scrap 148, if so then shame on you. You can also use two ITT410 out of a scrap Cybernet radio and that...

Animal

Of course they do Dave

Animal

I had a similar problem with a Cobra 148 It had been modified to cover extra frequencies & one of the diodes had gone - no matter how far I adjusted the pots I couldn't reach the offset frequency :doh: You didn't say if your Jumbo is modified but maybe worth checking out before starting to look ...

Animal

zodiac wrote:What MOD Steve ?.

Dave - It's a great idea using the MC145151 to get 5kc steps rather than waiting for someone to call on the zero's then calling them back!

Would it tune continuously or would it still need a 10kc shift added to get the alpha's?

Steve

Animal

Cheers Dave,

Scrap Cobra 148's - perish the thought!!!

I've got a RD16HHF1 MOFET (sealed in anti-static package) if you want to do a swap for some varactor diodes?

Steve

Animal

Dave

I wouldn't mind this mod doing to a President Grant (PC-999AE)

Will it still need a +10kHz shift adding (it's standard at the moment) or does it step 5kHz continuously after the mod?

Cheers

Steve

Animal

Radio Make and Model: President Grant (Black Front) PCB Number: PC999AE PLL Number: Test gear available: Stand Alone Counter, Digital VOM Symptoms: Coarse clarifier control doesn't shift 5kc either side. What is working: Everything else works fine. What has been tried: Nothing (I'm just a keen hobby...

Animal

Dave/Ray I checked TP2 voltage on Hi band (Ch40 AM mode) & it was 7.4v I adjusted L18 for 5.4v (Hi Band CH20 AM Mode) & base voltage has dropped to 7.1v Re-checked final & driver bias (both within spec at 51ma) Hope I'm going in the right direction??? Sounds okay on my other receiver (bu...

Animal

Dave

Checked driver & final base (mike gain fully anticlockwise on SSB) & I get 0.73v & 0.69v on TX

Steve

Animal

Checked screws - all tight & solder tabs all intact. Noticed that the problem seems to occur on Hi Band setting only (especially noticable when the 'bleep' goes off - it is distinctly 'bubbly' and not a stable tone) but I'll need to get this confirmed by another station listening to the audio on...

Animal

Radio Make and Model: Cobra 148 GTL DX PCB Number: 010AA PLL Number: Test gear available: Digital VOM, Stand Alone Counter, Symptoms: Audio on SSB is distorted (like I'm gargling with gravel) What is working: Everything else is fine. What has been tried: Checked biasing, checked offset adjustments, ...

Animal

It's not just your set they all have some RF floating about but it doesn't cause any problems normaly. Anyway, your now Animal the RF tamer. :D Dave. I might be able to tame RF (or even lions with an upturned chair!) but still haven't managed tame the wife's spending :doh: I've started another thre...

Animal

zodiac wrote:What make is the radio ?.

It would appear to be a Connex with a SC2290 final or four SD1446 finals

Personally I'd have the power turned down to a reasonable level if you want it to last longer than three months

Animal

It's thirsty work watching you so I'll bring my own water & tea bag next time

Animal

Dave,

I didn't have a power mic attached.

Mic gain was set fully anticlockwise.

Fitted the jumper wire as you suggested & all is now good thanks

By the way, why would I be getting stray RF with this set?

Steve

Animal

It may be worth mentioning that I've changed the driver & final in this radio to 2SC2166 & 2SC1969 respectively (Eleflow) I had to back-off VR12 ALC as the RF meter was pegging full-scale on ssb with mic gain at 12 O'clock (& TX audio was distorted) May have no significance but you never...

Animal

Dave,

You're correct - it stops when I lift the top lid

What's all that about then & how did you sort a permanent fix (other than the end-crust from a loaf of Hovis wedged between lid & chassis!)

Cheers

Steve

Animal

Oh & his tea making skills, well, err.........., the least said about that the better!

Animal

Radio Make and Model: Cobra 148 GTL-DX Mk2 PCB Number: 010AA PLL Number: Test gear available: Stand Alone Frequency Counter, Digital VOM Symptoms: I have a full carrier on USB/LSB (drawing 2.5A) What is working: Everything else seems fine. What has been tried: Adjusted VR7 which has no effect whatso...

Animal

Just a quick word of thanks to Dave (Zodiac) for his kind assistance with a poorly rig. Like other technical helpers, he devotes a lot of time & effort to the hobby helping less knowledgeable folk (like me!) without being impatient & condescending. =D> Thanks again Dave - you're a true gentl...

Animal

For all intents & purposes they're both baseloaded quarter-wave mag-mounted mobile antennas (capacitively coupled to the bodywork of the vehicle - this means there's no metal to metal contact!) & will be much of a muchness - anyone who claims they see two or three S units difference is talki...

Animal

Philip Do you have a trickle charger connected to the battery all the time? If not, I'd consider it. I found that when I was mobile using a KL-500 I needed to have the engine running (with alternator charging the battery) otherwise I'd get 'distorted audio' reports - those things could draw well ove...

Animal

Have you adjusted RV116 as well as the coils L131,L132. L133, L134???

Animal

Phillip If you TX when the switch on the amp is in the FM position, it doesn't damage the unit. The FM/SSB switch just activates the delay on SSB (or de-activates it in AM/FM mode) Are you running the amp mobile or homebase? If homebase, what PSU are you using & how many amps can it deliver? Wha...

Animal

Try turning down the AM TX power to 4W and see if the AM TX audio comes right, 10W is too much, if the power output does not change when the VR as adjusted it gives a clue as to where the problem may be. Cheers Scott (I should have noticed that :doh: I suppose the logic being that there's no room t...

Animal

Animal, Have you adjusted the AMC VR2 front right corner ?. Dave. Thanks for the reply Dave. Tried that today & still sweet FA! Output must be milliwatts in ssb - the needle just to say moves on the inbuilt & an external meter. Definitely audio on another receiver when TXing into a dummy lo...

Animal

Radio Make and Model: Stalker IX PCB Number: PC-385 PLL Number: Test gear available: Digital Multimeter, Frequency Counter Symptoms: Very low, almost inaudible TX audio What is working: Everything else. What has been tried: Adjusted VR7 (ALC) with no change to symptoms Did it suddenly happen ?: Don'...

Animal

Did you recalibrate the meter after increasing the power?

Animal

In a word 'No' This phenomenon normally occurs with a transceiver which has had a PLL synthesizer alignment without letting the radio warm-up first. As per the alignment procedure, put the clarifier control(s) in the center detent, then re-adjust offsets. You'll need a stand alone frequency counter ...

Animal

Okay - thanks.

Animal

Sorry for the late update Dave, I did sort it eventually by removing the mod for the extra bands (it's back to standard three blocks of 40) So I guess you were correct about the diodes - thank you for your patience. Unfortunately, I've uncovered another problem which may or may not be related. When ...

Animal

Okay, I managed to measure voltages either side of the diodes:

They're all approx. 8V

Cheers,

Steve

Animal

Is there an easy way to get to the diodes Dave???

They're right underneath the channel selector mechanism/ribbon cable & it looks like the front has to come off???

Many thanks,

Steve

Animal

Try Durham Radio:

10-1380 Hopkins St., Whitby, ON Canada

They used to carry AV-122 & AV140 spares.

Animal

Changed IC6 - both adders now replaced.

Voltages at PLL still the same

Any ideas where to go next???

Animal

Changed IC7 and checked voltages on PLL

They're just as they were - no change at all.

TP3 still reads 17.920 (should be 16.490)

I'll change the other adder (IC6) & report findings later.

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