[Drake] R-4C Alignment Question

[Garey Barrell]

Dan -

Electrically, you are connecting 10k resistors across the plate
inductor of the Premixer stage and the transformer driving the
First Mixer grid.   The idea is to simulate the loading of the
Injection cable and associated circuitry, so you can align the
receiver by itself.  Personally, I cable the receiver and
transmitter together for normal operation and do the alignment.
I find that even using the resistor method, the transceive levels
are still variable, and I end up having to touch up the injection
adjustments with the cabling in place anyway!

Doing the alignment this way also debunks the "you gotta use
RG-62 coax" nonsense as well.

RG-62 = 93R = 13.5 pF/ft = 0.240" o.d.
RG-58 = 50R = 28.5 pF/ft = 0.193" o.d.
RG-59 = 75R = 14.8 pF/ft = 0.242" o.d.
RG-6 = 75R = 16.2 pF/ft = 0.270" o.d.
RG-174= 50R = 30.8 pF/ft = 0.110" o.d.
Mic Cable (Belden 9456) = Hi-Z = 12 pf/ft = 0.160" o.d. (foam poly)
Mic Cable (Belden 8421) = Hi-Z = 16 pf/ft = 0.180" o.d. (foam poly)

The characteristic impedance of the cable is of no consequence,
only the shunt capacity of the cable. I'm sure you will have
someone tell you that you MUST use RG-62 for the interconnect
cables, but as you can see from the above list, this is NOT true.
  I put this right up there with the "oxygen-free copper" wire
that "sounds so much better" in audio setups. Aside from being
twice as thick and ten times as stiff as mic cable, RG-62 is a
pain. It has a very low temp insulation and it is difficult to
assemble cables without generating internal shorts.

73, Garey - K4OAH
Atlanta

dmartin wrote:

> In a related question, what purpose is served during the alignment process in 
> temporarily connecting resistors to these contacts? I do not have the manual 
> in front of me, but I recall one resistor goes from contact to ground and 
> another jumpers the other contact off to somewhere else?
> 
> Dan
> 
> On Wed, 19 May 2004 10:06:33 -0400, Garey Barrell wrote
> 
>>The rotor contacts are the "longer" ones that are always in 
>>contact with the "blade" of the switch.
>>
>>They are the ones with the small, air wound coils connected to 
>>them, and a lead to either T3 or T4.
>>
>>73, Garey - K4OAH
>>Atlanta
>>
>>Bill Jackson wrote:
>>
>>>Greetings,
>>>
>>>Can someone tell me which are the "green" colored rotor contacts on 
> 
> sections
> 
>>>S1D and S1E of the band switch on an R-4C?  The coloring is gone on mine,
>>>probably due to switch cleaning with alcohol.  I would like to touch up 
> 
> the
> 
>>>alignment per section 5-12 of the manual.
>>>
>>>Thanks!
>>>
>>>Bill, K9RZ
>>>