[CW] CW Keyer Interface

Thu Oct 29 06:35:04 EDT 2015

Thanks Rob. I am not game to open those kinds of msgs, so have sent it into 
the ether.
regards fm Me

----- Original Message ----- 
From: "David Wescombe-Down" <d.wd at bigpond.com>
To: "CW Reflector" <cw at mailman.qth.net>
Sent: Thursday, October 29, 2015 4:50 AM
Subject: Re: [CW] CW Keyer Interface

> 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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