[Drake] Re: TR-4CW/RIT PTO

[Garey Barrell]

Dale -

OK.  That sounds more like what I would expect.  The 3 hour warm up is 
most likely a result of the fan.  Without the fan, it would probably 
stabilize much quicker, but certainly the fan buys you much more than it 
"costs" you.  On the other side, the fan will definitely reduce the 
"transmit" variation normally seen when the additional heat would 
normally raise the cabinet temperature significantly on each transmission.

I think the insulation will probably make no difference other than to 
stretch the warm up time further!  Insulation is primarily effective 
when you are trying to keep the temperature caused by INTERNALLY 
generated heat INSIDE the insulation.  Insulation against OUTSIDE heat 
will only lengthen the time it takes for the PTO to reach equilibrium.

Sounds like if you plan to run the fan, and you need super stability, 
you'll just have to allow for a longer warm up time.   Or, use the RV-4 
to control the frequency during warm up.  It probably stabilizes within 
10-15 minutes as long as the room temperature is reasonable.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>



DALE PARFITT wrote:
> Hi Gary,
> Good information. The RIT was off. And later I varied my Variac ( I 
> run the TR-4CW/RIT on a Variac as my line voltage is a bit high here- 
> and likely a lot higher that the early 70's) and saw no change- so I 
> would guess you are correct that the zener in this case does a nice job.
> After 3+ hours the rig settled down to +/- 10Hz or so every 1/2 hour- 
> which is more than acceptable. In fact after 4 hours, she was back to 
> the start frequency and staying there.
> Now that I have some hard data, I think I'll make  a blanket out of 
> 1/4" polyethylene foam and see if that buys anything.
> Stay tuned.
>
> Dale W4OP
>