[CW] CW Keyer Interface

Wed Oct 28 14:20:00 EDT 2015

Can't help with a "keyer interface" cos I don't use a keyer, but I do use 
both HB Cootie & Vibroplex Champion bug with HB electronic TR switching & HB 
electronic isolation for my amplifiers.

The 833A amplifier for 630m is driven by an ex-marine Belgian SAIT-150 xtal 
controlled tx: 10/30/50W selectable & the diode TR switch is built into a 
small project box to take the place of whatever was the TR device in the 
original marine rx that was hard-wired to the tx. There are no bitey volts 
on any key used for that circuit.

As a separate station, I have a pair of 813s monoband for 160m & driven by 
either a Drake TR-7 or locally produced Codan Envoy SDR txcvr (for which I 
conducted all the on-air CW testing for Codan).
As another separate station, I can run the TR-7 or Codan to a Drake L4-B HF 
amplifier.
No bities on either of those either.

The 813 amp & L4-B have different keying voltages, 12 & 30, so I didn't want 
the 12V componentry having to look @ 30V coming at it, & another simple 
diode isolation unit in a little project box takes care of that.

In this way, I can have all 3 separate stations spread across about 8 feet 
of desktop, all amplifiers flashed up to go, & move from one setup to 
another by just switching aerials via coax switches (one for equipment & a 
Heathkit D1234 for the aerials, dummy load etc)

Both 630 & 160m have separate RG58 coax feed to my 170ft Inverted-L (see 
RSGB "RadCom" Oct/Nov 2015) over 60 radials & there is also a 170ft 
doublet-fed flattop actually an EDZ for 40m) that I can switch for either; 
160m tx, 630/160m rx option, HF or whatever I want. In the HF switching for 
it, a kilowatt version Johnson Matchbox lurks waiting to do its job & when 
used on 160m I have a big monoband link coupler in line: all bases covered & 
works a treat.

Each coax switch & each isolating unit is separately earthed, as well as via 
the SO239/PL259 hookup arrangements. No stray RF floating around & I am 
working Stateside, Europe etc (better than 15 000 miles so far) on 160 after 
dark here; all across VK-land on 630m (over 3000 miles) & am just waiting to 
catch some Oceania stations on that band.

I can't suggest any commercial keying isolators etc cos I don't buy stuff, 
but I hope the general ideas above may be of use to someone. If not, delete 
this!

cheers all from Down Under

Dr David 'Doc' Wescombe-Down VK5BUG
On CW since 1964!
FISTS 14136 SKCC 6897 QRZ.com
"MF Morse operators are good with their hands after dark!!"

----- Original Message ----- 
From: "Donald Chester" <k4kyv at charter.net>
To: "'CW Reflector'" <cw at mailman.qth.net>
Sent: Thursday, October 29, 2015 3:15 AM
Subject: Re: [CW] CW Keyer Interface

>> Does anyone on here know of an available keyer interface (built or in kit
> form) to interface
>> a modern ss keyer to a cathode keyed transmitter?  Something good for 800
> volts @ around
>> 300 ma or more? I'd also use it with a semi-automatic bug to get the high
> voltage and current
>> off of the bug or straight key.
>> All my modern keyers around here are OK with QRP rigs and the newer
> transceivers,
>
>> but they can't handle cathode keyed transmitters. Right now I'd like to
> use my Eldico TR-75 TV transmitter as I had one as a kid > back in 1953. 
> I
> think I need an interface to use my keyer.
>
>> Anyone have any suggestions.?
>
>> Lee, w0vt
>
> I homebrewed mine using a TV sweep transistor, a stripped-down version of
> the circuit described in the 1981 ARRL handbook, page 11-2. You should be
> able to find the same article in other editions, give or take a few years. 
> A
> detailed write-up of my circuit, including schematic, appears in August,
> 2014 Electric Radio, page 6.  I used an ECG 238 as the keying transistor,
> driven by an ECG 129, purchased at the local electronics store. The ECG 
> 238
> was a little pricey when I bought it, but it will handle up to 7 AMPERES 
> of
> cathode current at 1500 volts, leaving plenty of safety margin for about
> anything I would ever want to run. I built it in the mid-1980s, so I don't
> know if those transistors are still available following the demise of
> picture-tube TVs, but if not, suitable substitutes may be available or the
> sweep transistor could be salvaged from a junked TV.
>
> Mine works very  well with my bug or the electronic keyer I built up 
> around
> one of those little Curtis IC chips.  I use it with both my homebrew
> transmitters, in which the keyed stage runs about 40 ma at 600 volts, and 
> on
> 160m with my converted Gates broadcast transmitter that uses a pair of 
> 807s
> in the driver stage, 650 volts at 200 ma.
>
> I didn't find the R-C key click filter described in the Handbook article
> very effective, so I added the standard key click filter for cathode keyed
> tube type transmitters, using a choke, capacitor and resistor as described
> in all the Handbooks from the 1930s through probably the 90s or early 
> 2000s
> (I don't find much useful information of any kind in the later editions).
> The filter is inserted between the sweep transistor and the cathode of the
> keyed stage.   At first, I was a little worried about inductive kick-back
> from the choke destroying the keying transistor, but that hasn't been a
> problem.  The R and C components in the filter circuit appear to take care
> of that, plus the voltage rating of the transistor is probably high enough
> to withstand any spike that  would ever occur.
>
> One problem I have encountered with cathode keying an intermediate  stage 
> in
> a couple of my transmitters is back-wave, when only one stage was keyed. 
> In
> one of my homebrew transmitters I key a single type 802 tube, and got rid 
> of
> the backwave by neutralising the 802.  In the Gates, with a pair of 807s
> driving a pair of 833As in the final, I key the 807s along with the 12BY7
> stage that drives them and the backwave disappeared.
>
> Don k4kyv
>
>
>
>
> ---
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> =30= 