[ARC5] SCR274 improved with zener or glow tube?

[J Mcvey]

Bill,It's a SCR 274 standard setup, including the BC442 antenna relay. So,whatever loading occurs there happens anyway whether I use it to monitor the TX or use the original side tone oscillator config. The receivers antenna is grounded, but there is no other muting mechanism other than the audio is normally switched over from the rx over to the  BC456 side tone. Thwarting that function requires no mods other than just not hooking up the sidetone cable to the rx rack.
The local tx leakage is loud enough to hear, but by no means overloading the radio.If I didn't monitor it, I wouldn't know how bad it was! Maybe I'll use the side tone once I am satisfied with the way the tx performs.
I also noticed that the chirp could be reduced with looser coupling and lower power- but that's no fun! I want to "give 'er all she's got, Scotty!"


 

    On Sunday, March 20, 2016 5:11 PM, Bill Cromwell <wrcromwell at gmail.com> wrote:
 

 Hi Jim,

You may already be familiar with how receivers can react to very strong 
signals at the antenna while using them to monitor your own transmitter. 
Depending on how much "leakage" is applied a receiver can cause *all* of 
the chirp, whoop, and yoop or add to whatever is already made by the 
transmitter. Shorting the receive antenna terminal to ground is enough 
for QRP operation but more reduction will probably be needed for higher 
power.

I prefer separates with the receiver monitoring the transmitter output 
instead of 'sidetone generator' or silence. Instead of 'muting', the 
gain has to be reduced during transmit and can be done fast enough for 
full break-in - aka QSK. If too much signal gets in or receive gain is 
too high the receiver will make even the best TX sound like crap.

I am sure the regulation in your transmitter will help. But don't 
overlook the possible RX contribution.

73,

Bill  KU8H


On 03/19/2016 09:35 PM, J Mcvey via ARC5 wrote:
> I have been thinking of how to further iron the chirp out of my CW on 
> the 12V converted system.
> Getting a better 12 dyno helped somewhat, but there is still more 
> chirp than I want to hear.  In fact I'd call it more of a slur or whoop.
> The first key down is the worst, but if I keep a steady CW flow going, 
> it averages the supply voltage and it sounds better.
>
> One of the non-standard things here is that I use the leakage 
> radiation into the rx to monitor. I can still do it this way when I 
> get the modulator set up (28v) by simply omitting the sidetone cable 
> for the bc456 that switches the audio. Good idea, or not?
>
> Has anyone tried a zener or glow tube to regulate the the OSC supply? 
> Did it work?
> I have heard old MOPA rigs that only had a hint of chirp which is fine 
> by me. How do I attain this goal?
>
> Jim, AC2EU
>

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