[Drake] R-4B to T4XC connection

[Al Parker]

Hi Howie,
	Garey, K4OAH, has put out the following several times in the last 10+ 
yrs. I saved it in 2006 & 2011.
Al
==========================

All original cables were 38" long tip-to-tip.

The INJ, (and CAR OSC in the C-Line, cables used a foam inner dielectric 
and phono connectors with a white insulation.  This cable measures 60 pF 
total capacity.

All other cables used the standard for the day clear polyethelene inner 
dielectric and phenolic (brown) insulated phono connectors and measure 
~100 pF.

Original Drake INJ and CAR OSC Cables = 19 pF/ft = .160" o.d. (foam poly)

RG-62 = 93R = 13.5 pF/ft = 0.240" 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 8410) = Hi-Z = 33 pf/ft = 0.160" o.d. (foam poly)
Mic Cable (Belden 8421) = Hi-Z = 16 pf/ft = 0.180" o.d. (foam poly)
R/S Audio Patch Cable = 28 pF/ft = 0.165" o.d. (poly)

The best choice is the Belden 8421 Audio cable from their "Brilliance" 
line.  It looks just like the other cables, and is very flexible.  The 
RG-62 is OK, but it is 50% larger and far less flexible.  RG-62 is also 
prone to shorting if bent over too small a radius, and is susceptible to 
heat damage when soldering connectors.  The best "feature" of RG-62 is
that it is often FREE, since there have been many miles of it pulled out 
of old computer networks.  Belden 8421 is available by the foot from ACK 
Electronics in Atlanta.  Other distributors have it as well, although 
many require purchase of a full spool.  N7IOH, another list member, had 
some at one time that he was selling by the foot.

The only pertinent factor is the total capacity.  Impedance and "loss" 
are not important.

Any  _reasonably low capacity_  coax will work if the units are cabled 
together for the adjustment of the INJ trimmers.

The cable type ONLY affects the LEVEL of the PreMix signal, (5.645 MHz 
ABOVE the transmit/receive frequency,) and a small DC control voltage 
between the two.  If the shunt capacity is too high, insufficient LO 
level for the first mixer will reduce the sensitivity of the receiver 
and the output power of the transmitter.

Some of the "commercial" cable mfrs use RG-59A, but it's a little larger 
and also prone to shorting if bent over too tight a radius.

The ANT lead to the receiver is too short to matter, but you want good 
shield integrity, which usually eliminates R/S cables.

The best connectors I've found are the Switchcraft 3502 plugs, available 
from just about anyone, Digikey, Mouser, Allied, Newark and just about 
any reputable parts place.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
=====================================================


73,Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 1/9/2017 4:32 PM, howard holden wrote:
> I've got an R-4B and a T-4XC that I want to hook up to transceive. I
> note in the T-4XC manual they talk about low capacity cable for the
> oscillator injection, but I don't see where the type of cable is
> specified. Any help on this? Cable lengths?
>
> Thanks
>
> Howie WB2AWQ/7