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 Post subject: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 2:26 pm 
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Last edited by Mikeinkcmo on Jan Fri 25, 2013 7:28 am, edited 1 time in total.

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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 3:18 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1813
Location: Potomac, Md.
Johnson did believe in line filtering, didn't they? Love all those little inductors and caps! Reminds me of the underbelly of the Ranger that got me through my General ticket years in the '50s-early '60s. I think the Ranger might even have had two LC sections back to back.

But that was back when TVI was a real problem if you operated on 15M, close to the TV IF frequency, which I dimly recall was 21.25mc. Hence the Ranger's copper fingerstock and meter shielding in addition to the line filtering.

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Avery W3AVE


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 3:40 pm 
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Posts: 16550
Location: Somers, CT
Hi Mike

I always wanted to homebrew one of those. Can you tell me what the RF transformer looks like, and how it
is constructed? EFJ didn't provide much information on the turns ratio, etc. Looking at your print, T2
almost looks like it could be a RFC with a tapped winding, looks to be 2500uH or so? Can you see if
was tapped, or did they add a winding over the pi wound coil?

BTW, I'm sure you know this, but that should be located as close to the TX as possible, since they used
the PA tuning for the T-R Switch input tuning. I don't know if you're planning on a HT-32, but I surmise
the Johnson T-R switch won't work with that TX because the driver and PA stages are biased in AB1
whenever the transmitter is turned on... I'd expect too much white noise is being generated
during standby. The manual mentions that is a concern with some TX modes, but no specific examples
were given.

The switches also generated harmonics, so most hams used a low pass filter in the line before the
antenna. W8JI did an analysis of the switching time on his website; it is also not a good mate for
a solid state RX.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 4:16 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 6069
Location: Santa Rosa, CA
Quote:
The problem of receiver audio muting during transmit, still needs to be addressed though.


I used the Johnson T/R for years with my DX-40 and NC-109 on AM. I had an external PTT relay that keyed the transmitter and disabled the receiver. The NC-109 had an accessory socket on the back that gave access to the receiver, but I can't remember if it killed only the audio or the whole B+ ??

And, yes, I did have a low pass filter installed. My family still talks about watching JFK on TV when he said:
"My fellow Americans... CQ 15.... CQ 15."

Rich


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 4:24 pm 
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If Mike does get a HT-32 (and I'm doing my best to spend his money :mrgreen: :mrgreen: :mrgreen: }
it has aux. relay contacts on the rear 11 pin connector for RX muting.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 5:11 pm 
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Last edited by Mikeinkcmo on Jan Fri 25, 2013 7:29 am, edited 1 time in total.

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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 5:38 pm 
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duplicate, reposted instead of edited.


Last edited by Peter Bertini on Jul Thu 21, 2011 5:43 pm, edited 1 time in total.

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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 5:42 pm 
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Mike

It might be easier to lift the ground return on the bias pot in the HT-32 to bias the finals into
cut-off. But.... I vaguely remember that the high B+ on the 6146s soared to uncomfortably
high levels when the supply was unloaded--especially at higher line voltages.

I think that's what scared me off on doing any mods of that nature. HT-37 and HT-32
are of the same ilk... HT-37 cut back on the frills (cast metal bezels, etc.) and dropped
the crystal filters for a phasing type SSB generator. Otherwise the electronics are pretty
much the same.... HT-32 is prettier and matches the SX-101 series, but lacks 160 meters.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 6:02 pm 
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Joined: Oct Sat 20, 2007 3:36 am
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Location: Southern NH, 03076
I have two Johnsons, one each on a Viking I and II with and without an amp. There are also two B&W's that handle the HT-9's and whatever else I want to use and Im looking for more. Trying to get rid of all the Dow Keys.

Since I operate only with headphones muting isnt an issue and no receiver front end coils have been harmed performing these tests :lol:

The vintage SSB stations each feed a NCL-2000 which have built in relays and inputs for seperate TX/RX there is no problem there either.

Carl


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 6:49 pm 
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I'm sure I'll gravitate to T-R switches on the two B&W 5100s that are sitting
on the shack floor waiting for me to finish the new shack operating table.
Those Johnson TR switches have gone out of sight price wise. But I keep
watching for one that slips by for under 50 bucks.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 9:54 pm 
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Johnson also made a "companion" the Signal Sentry. It handled the audio muting and generated a separate "artificial" cw note for monitoring. I used the pair for many years with a Heath Apache/HQ170. Still have them! The red pin jack on the T/R switch feeds the Sentry.

Image


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 10:32 pm 
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Pete,

T2 appears to be a powdered Iron(black) core about an inch and an eighth O.D., the coil is single layer 15T with the tap at 3T, #26 enameled wire.

Should I be expecting progress "pics and story at ten"? 8)

Bill,

I'm going to run the "probe" to my gates modulation monitor, and from there to the bench oscilloscope.


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 10:37 pm 
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Hi Bill

That photo looks very familar. Is it featured on a website you
own?

Mike, the SX-101A is on the floor next to the bench; I've had a
continuous stream of outside work that's been keeping me from
my own projects. But, if I can tempt you into spending more
money you can bet I'll be posting photos of the SX-101 and
HT-32 when they are finally together in the cherry wood cabinet,
LOL. Seriously, I'm getting anxious to see them both up and
running.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Thu 21, 2011 10:43 pm 
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Location: West Salem, OH
Peter Bertini wrote:
Quote:
But I keep watching for one that slips by for under 50 bucks.


Under $50?! :shock: I think I might still have one in my pile unless I tossed it. I was told it was working but maybe like 20 years ago I hacked the power cord off as I was going to toss it then. Needed the cord for something can't remember. Go figure they are worth a bundle now! :o

Bill

P.S. Come to think of it I think I remember seeing the silly thing when I found that meter for graylox.... Maybe I can find it a home..


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Fri 22, 2011 12:31 am 
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KB8CWB wrote:
Peter Bertini wrote:
Quote:
But I keep watching for one that slips by for under 50 bucks.


Under $50?! :shock: I think I might still have one in my pile unless I tossed it. I was told it was working but maybe like 20 years ago I hacked the power cord off as I was going to toss it then. Needed the cord for something can't remember. Go figure they are worth a bundle now! :o

Bill

P.S. Come to think of it I think I remember seeing the silly thing when I found that meter for graylox.... Maybe I can find it a home..


Let me know what you want for it if you decide find it a home.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Sat 23, 2011 2:27 am 
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Greetings, All!

It would seem that most of you appear to be missing the point.... the Johnson electronic TR switch is intended for a specific application.... namely fast break-in CW. You are supposed to hear yourself (side tone) but the idea is that any other station's CW signal can be heard in the gaps between your characters, or even between your dots and dashes. The receivers of the day were operated with no AGC (volume control set to max and volume controlled with the RF gain pot) when receiving CW (BFO in use) so receiver recovery time was not an issue. There is absolutely no point in using an electronic TR switch for any other mode of operation, as conventional TR schemes are superior for voice work.

73,
Jim T.
KB6GM


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Sat 23, 2011 4:15 am 
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In the receive mode, the TR switch also acts as a RF amplifier raising the noise level of the receiver. If you're listening to a strong AM signal between the frequency operating range of the TR switch, it can add distortion to the signal. Personally, a good old fashion relay, works a lot better, and can have additional contacts to do additional switching if needed.

Pete

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http://www.manualman.com


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Sat 23, 2011 5:12 am 
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The HT-32 has been modified for semi-break in CW. I'll take a small trade-off on the
receiver rather than hearing a Dow Key clanking its brains out between characters.
The way the HT-32 is designed, spare contacts on the internal relay are used to key the
antenna relay. The transmitter is at full RF power almost instantaneously when the CW
key is closed, and the antenna relay ends up hot switching RF because the sequencing
is wrong and the mechanical delays.

For the B&W 5100 TXs on phone, it might be a valid point that a T-R switch won't offer
much over an external relay.

Pete


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Sat 23, 2011 7:45 am 
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Joined: Oct Sun 11, 2009 10:06 am
Posts: 1441
Location: British Columbia
Cool little electronic t/r switch Mike. I used to build those right into some sets. I just finished a t/r box for a fellow ham. Very indepth, long term project. (glad its over :) )


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 Post subject: Re: E.F. Johnson electronic TR Switch
PostPosted: Jul Sat 23, 2011 2:40 pm 
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Joined: Oct Sat 20, 2007 3:36 am
Posts: 14393
Location: Southern NH, 03076
In the 50-60's many used them on AM with no problem and on 10-20M the slight bit of preamp gain was a big help on just about anything using octal tubes or an otherwise basic front end.

With the Dow Key noise and often sticking receive side isolating contact it was a pleasure to get rid of them.

The B&W 381 series had a band switch and later versions had a tuning control which both improved image rejection a bit and could be detuned as a gain control on the lower bands. Mine are both the 381C.

Carl


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