[Milsurplus] [MMRCG] Bendix Skipper 135: Spooky Radio Hi-Jinx on Halloween!

[Ray Fantini]

Instead of installing a capacitor and the like maybe a better installation would be to install a coaxial jumper in the back of the radio that allows you interrupt the connection between the T/R relay K2B and the input to S1-G so you can keep the original loading section for use with a short antenna or access the input and output of the radio directly after the T/R relay?  Everything after S1-G is just for matching the short antenna and I always felt that that’s the biggest advantage to that radio allowing it to work with a short antenna or whip at Ham fest or other events so why try to compensate with a capacitor to get to Z=50 when it may be easy to just go before that mess that they built into the radio for a high Z output? That may also help the receiver too.

Ray F/KA3EKH



-----Original Message-----
From: MMRCG at groups.io <MMRCG at groups.io> On Behalf Of David Stinson via groups.io
Sent: Sunday, October 31, 2021 7:27 PM
To: Boatanchors at mailman <boatanchors at mailman.qth.net>; milsurplus at mailman <milsurplus at mailman.qth.net>
Subject: [MMRCG] Bendix Skipper 135: Spooky Radio Hi-Jinx on Halloween!

CAUTION: This email originated from outside of Salisbury University. Please exercise caution when clicking links or opening attachments from external sources.


Halloween, and the Zombie
Bendix Skipper 135 "fishing boat radio,"
which some said had not a ghost
of a chance of resurrection, though it had neither been staked nor stuffed with garlic, lives!

Despite the grumblings and howlings from assorted witches and werewolves, I applied Black Cat Bone, Eye of Newt, Toadstool and Solder Rosin, reciting sea shanties and Behold!
With a whiff of salty sea breeze, it arose from the Land of Undead Radios and made its first ham contact, saying "Boo!" to the gang on 3890 KC, pushing my 30L1, glowing like Frankenstein on a dark and stormy night.
https://photos.app.goo.gl/25oQLPLRXw6txKve7

Yeah, yeah ok... I couldn't resist.
On to business, because this radio
is "spooky enough" for Halloween.

The Skipper 135 is a mid-1960s hybrid "Marine" HF AM transceiver capable of xtal-control operation from
1.8 MC to 5 MC. and, like many WWII radios, was designed to work into an electrically-short antenna.
The receiver and audio/modulator are all-Germanium PNP transistors.  The transmitter is a 12BA6 crystal oscillator feeding a single 12DQ6 power amplifier with a PI-L output network.  The front panel claims "33 Watts,"
which may be an inaccurate allusion to PEP power, since the radio actually delivers about 25W carrier to the antenna.
I haven't scoped the output for PEP yet.
The SAMS folder which contains the Bendix Skipper 135 schematic is available at:
https://drive.google.com/file/d/1Wg1VrsNaw1jykO3srpftl4zKot0z7hKk

Unlike with historic military radios, I don't have a big problem with *well-thought-out, informed* modifications of radios like this to make them functional on the Ham bands.  I've changed the output connector to an SO-238 and added 100pFd in series with the antenna lead to match the set to a 50-Ohm load, removed the 10pFd trimmer from the back panel to make room (not needed for 50-ohms), and changed two of the xtal sockets from HC-6/U to FT-243.  I will also be installing an aux relay which will provide a keying lead to an external amp, plus a switchable power buss to Programmable Oscillators/amps for the Xmtr channels.

Here comes the "spooky" part:
Take a look at the Modulator/Audio output stage (upper right of the diagram).
While foozilin-around, looking for a good Prog-Osc solution, I managed to pop the Audio Preamp Q5 and the TO-3 Driver Q6.  I had a nice Motorola TO-3 Germanium, but my stock of small-signal PNP Germaniums is getting kinda thin.  I decided to see if I could make a PNP silicon, 2N3906, work in the stage.  I plugged it in, ready to read voltages, but the thing WORKS.
It plays with no changes, no distortion.
Later, while investigating prog-osc options for the receiver, I accidentally over-drove Q1 crystal oscillator and popped it. A 2N3906 worked, drop-in, no changes.  It will also work in the Mixer stage, though not so well when plugged-in as 1st or 2nd IF amp.  Photos:
https://photos.app.goo.gl/bv3T6m5NB5TVe5Ys7
https://photos.app.goo.gl/uLxDqdgo1vgpkBLH9

Silicon working in Ge stages, drop-in,
with no degradation of performance.
Now that's spooky...
Have you any Alchemical Insights into this mysterious happening?

Think I'll connect it to the Haunted Microphone for some late-night October 31st skullduggery:
https://photos.app.goo.gl/RK8p1KxiDvtC8Fjf7

Still digging in The Cave for ARC-5 relays for a list member (I've only found one- given most of them away- but still have a couple of stones to look under), so that's a good excuse to dig for the aux relay for the Bendix, when I can find some time for it.

GL OM ES 73 DE Dave AB5S