[Drake] R-4B to T4XC connection

[howard holden]

Thank you Gary and Al, great information. Sounds like an easy project to 
work up. I've got lots of short pieces of cable and RCA plugs, and 
knowing what they meant by "low" capacitance, I can measure some of what 
I have. I've even got sme RG174, and it looks like the 38 inch pieces 
originally provided are far longer than I'd need.

73, Howie WB2AWQ


On 1/9/2017 1:49 PM, Al Parker wrote:
> 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