[Premium-Rx] Notes on WJ-8715,8716, 8718 HF versions

[Terry O']

I sent this out on the Watkins-Johnson io group and though some Premium 
RX folks may be interested.


Unlike the WJ-8616, WJ-8617, WJ-8618 VHF/UHF radio series, 
Watkins-Johnson mostly did not put external markings denoting the 
different versions of the WJ-8715, WJ-8716, WJ-8718 HF radio series.  
Nonetheless, there are 35 versions of the WJ-8718 and 9 versions of the 
WJ-8718A and four versions of the WJ-8716.

The majority of these versions contain minor variations to meet a 
customer's needs. Some were trivial like the WJ-8718-3 that the NSA 
ordered a special AGC time constant for less distortion at low 
frequencies or the WJ-8718-22 which Sanders ordered as electrically 
standard but with a gray front panel and black lettering.

Others, like the WJ-8718-4 ordered by the FCC have great changes like 1 
Hz tuning and display resolution.  Or the WJ-8718-19 which is internally 
unique and tuned up to 100 MHz.  Or the even stranger WJ-8718/651S-1 
designed to be remote controlled by the Collins radio or a Delta RRC-1A 
(I know nothing about this Delta unit, so if you do, please let me know).

Among these there are only a handful with really obvious external 
differences like between the WJ-871x and WJ-871x/MFP and the WJ-871x/NAV.

The external differences between a WJ-8718 and WJ-8718A are minor, but a 
number of internal circuits were updated chiefly when certain parts 
became hard to get by the early 80s.  None of these are obvious unless 
you know your way around circuit boards.  Things like new IF switching 
circuits using 2N2222 transistors & MC1458 op amps instead of 3N187 
MOSFETs and in the RF amplifier where a WJ A50 monolithic amp replaces a 
scarce CP643 FET.

If you want to tease out the differences between the WJ-8718 vs 
WJ-8718A, the WJ-8718-17 manual (available for free download on my 
website) has duplicate schematics for several sections, with the second 
schematic noted "(Product Improvement)".  I've never located a WJ-8718A 
manual so this is as close as I can get on hard information (If anyone 
has a copy of an A manual and is willing to share, I have a comb binding 
machine and high speed scanners for duplex up to 11 x 42 inches and can 
return a loaned copy quickly).

One of the more obscure versions for which I'd like to get more 
information is the WJ-8716-2, which had a BNC on the rear panel bringing 
out the first IF at 42.905 MHz.  I'm working on adding this feature to 
my WJ-8718/MFP with the intention of connecting it to an SDR.  There are 
no filters prior to this IF (unless the radio has the PRE option) so the 
display will be much broader than the 455 kHz display with the matching 
WJ-9188 signal monitor or from the SMO option which is a 10.7 MHz output.

I'd appreciate any correction or additions to this information.

Best,
> Terry O'
> watkins-johnson at terryo.org
> http://Watkins-Johnson.terryo.org
> http://BlackRadios.terryo.org
> Facebook:   BlackRadios & BlackRadioSwap