[Milsurplus] ATD Transmitter

[wf2u at ws19ops.com]

Hi Marty,


Yes, that's why the series cap for all you explained down here (I also  
remember my RF design from my former career as an EE, although I make  
my radio play money in the IT field now...).
The reason behind the 100 pF I'm using is simply that I have a couple  
of 100 pF doorknobs I use with my other 50 ohm handicapped (cap?..)  
radios and I just borrowed one for the ATD.
Back to the bench on the weekend, I'll vary the cap by putting two in  
series for 50 pF or paralleling the two for 200 pF. One or the other  
should be close to optimum.
The unun is a 1:4 transformer which I made for the TCS years ago and  
tested on a network analyzer - 12 ohms unbalanced in and close to 50  
ohms unbalanced out. This works well with the TCS and the tuning for  
max is within the control range of the tuner in there.
Of course using it with the ATD may still require some Xc in there.
As to 30 W carrier out: on AM it'd make sense for 50 W input in to get  
in the range of the push-pull 6L6 modulator capabilities. On CW I'd  
expect more like around 70 W in and close to 50 W out. There is enuf  
grid current into the 814 to drive it to that power.
And no - I'm not making any mods in that transmitter. I just took out  
the cr*p which prevented it from functioning properly.

In the ATD, they could have used a pair of 807's for modulating the 814...

73, Meir WF2U


Quoting Marty Reynolds <cosmoline at aa4rm.ba-watch.org>:

>
> Yo Rian, Meir, Dennis, et al
>
> ATD seems to have link output.  The coupling  'D knob' on each TU.  So
> best procedure
> is to put a series variable capacitor in line.
>
> Why?  Delete NOW if ARRL Hbk electrical engr. gags ya.
>
> Here's why.  That series cap bucks the LINK's inductive reactance, Xl.   And
> that like Xc is frequency-dependent.  So there's no perfect little cap
> there to match
> 50 ohm ham loads.  Length of antenna, direction of toilet whirlpool, bird
> seed choice
> don't enter.
>
> The "D knob" swinging link acts  like an autoformer tap on the final's
> tank coil.  So an xtra transformer (unun? wherzat come from)?)  shudn't be
> needed.
>
> Last, 30W out.  That means about 50W input  which takes 6L6s to the limit.
>  I'd
> be a 30w happy boy  - hubba hubba hubba
>
>    signed
>
>      sr. wet blanket
>
> PS I like 814s & hence the ATD.  One thot is to use an 828 & run the 6L6s
> AB2 w.
>       two 9V batteries as negative bias.  Then 6L6s might make 50w & Meier
> you'll get
>       ur 60w
>
>       But be careful to keep basso profundo outa modulation xfrmr sr
> pavarotti
>
>
>
>
>
>