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 Post subject: Antenna Switch
PostPosted: Jun Tue 09, 2015 1:50 pm 
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Joined: Sep Sat 06, 2008 6:17 pm
Posts: 1167
Location: Central Pa, 17044
Hi guys, I am using a DX-DD 40/80M flat top antenna with my DX-60a /HG-10 VFO/ and an MFJ -969 antenna tuner.
My receiver is a Kenwood-R1000.
I seem to be getting out fine, but am not receiving the station on the other end.
The antenna I'm using on the receiver is a 20ft short-wave general coverage antenna.
My question is this... Can I switch the 40/80 meter tuned transmitter antenna over to the Kenwood receiver?
Other words, using the same antenna. Switch to transmit then back to receive.
What kind of Ant. switch would you get? Is there a homebrew, I could make?
Thanks for any help,
Gary/KB3WYZ


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 2:13 pm 
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Gary,

You can build your own T/R switch using a standard relay with 120VAC coil. A relay with two sets of contacts will suffice but a 4PDT (four sets of contacts) will be better.

Pin 5 of the accessory socket in your DX-60 supplies 120VAC when the transmitter is in transmit mode and is used to activate the relay.

One set of relay contacts is used to switch the antenna between the transmitter and receiver. Connect a line from a coax connector to the common contact of this first set and this is used to connect to the antenna. Connect another coax connector to the normally closed contact and this is used for the receiver. The final normally open contact is run to another connector for the transmitter.

I like to use another set of contacts with the common attached to the shield/ground of the connector used for the receiver and the normally open contact connected to the center/hot of the receiver coax connector. This set of contacts shorts the receiver antenna line on transmit providing additional receiver protection.

Another set of contacts is used to control receiver muting, Grounding pin 7 of the R-1000 remote terminal mutes your receiver. Connect a line from the common contact of this set to a cable running to a receiver grounding point (i.e. the ground connector of the remote terminal) and a line from the normally open contact to pin 7 of the remote terminal. This will automatically mute your receiver when the DX-60 is in transmit.

You can also buy a Dow Key type antenna relay which is easy to use because it already has the connectors mounted. However used ones may be very old and in dubious condition so use caution; new ones are very expensive. Make sure it has auxiliary contacts for receiver muting. For low power use I build my own T/R relays using standard "cube" relays with 5 amp or better contacts while I use vacuum relays for my high power setups.

Rodger WQ9E


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 3:21 pm 
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I will second Rodger.

Back when I was using a DX-60/HQ-129X I also wanted a way to switch antennas automatically. I could not afford a Dow Key switch so I made my own. I acquired a 3PDT open frame relay (120 VAC), a housing (which happened to be a vintage automotive voltage regulator - you could use anything), 3 SO-239 connectors, and an old sewing machine foot pedal (so I could have foot pedal changes from receive to transmit).

Then I mounted the stuff inside the gutted voltage regulator housing, and wired up the sewing machine foot pedal to just be a switch (instead of a rheostat), and connected things to the DX-60.

Here are approximations of the parts I used...
Attachment:
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imagesCAXX5BYL.jpg [ 8.62 KiB | Viewed 3561 times ]


On the relay I used one pole to switch antannas, one pole to mute the receiver, and one pole to actually key the Key input of the DX-60. The foot pedal was hooked between the DX-60 120 VAC accessory power and the relay coil. So every time I pressed the foot pedal it would energize the coil which switched the antenna to the transmitter, muted the receiver and keyed the transmitter.

If I wanted to run CW I disconnected the automatic switch from the Key jack and plugged in the Morse code key instead. I also eventually added a switch which would allow me to turn off the receiver muting so I could monitor my own CW with the receiver.

Curtis Eickerman

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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 3:53 pm 
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Very nice workmanship Curtis!

Rodger WQ9E


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 4:56 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 10939
Location: Santa Rosa, CA
When I was running my DX-40 and NC-109, I built a T/R relay which worked well. When I saved some money, I bought a shiny new EF Johnson electronic T/R switch. Worked very well.


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Rich


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 5:02 pm 
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Rich, W3HWJ wrote:
I bought a shiny new EF Johnson electronic T/R switch.
Eventually someone actually gave me a Dow Key TR switch (DKC-TRM-1) which was like the EF Johnson except without the internal power supply. I cobbled a power supply from an old radio, and was on my way with the new item.

For the uninitiated, these TR switches avoid the mechanical switching and have the receiver always connected to the antenna via a tube which protects the receiver from excessive power. Here is a schematic for the EF Johnson TR switch... http://www.w8ji.com/johnson_tr_switch.htm

You still have to deal with receiver muting via some other mechanism (again often a relay).

Curtis Eickerman

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Last edited by Eickerman on Jun Tue 09, 2015 6:15 pm, edited 1 time in total.

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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 5:41 pm 
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Joined: Jan Fri 13, 2012 6:52 pm
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Location: Grays Harbor, Washington
Hi Gary;

If I could add to the comments submitted, I might have you try a video I made last year.

https://youtu.be/ikLJ5ms9NBM

Your DX 60 has a switched 115 volt AC output when you go into transmit mode.

The best bet would be a dow key relay with a 115 volt AC coil.

Pins 5 and 6 on the accessory socket supply voltage while in the transmit mode which will activate
your relay.

Make darn sure you count the pins from left to right if you are facing the socket from behind.

You might also want to download a copy of your transmitter for reference.
If you don't have a copy, go here; http://www.vintage-radio.info/heathkit/

If you just want to buy a dow key relay, you might try Ebay.


This is what one looks like. http://www.ebay.com/itm/DOW-KEY-FA-9792 ... 33a409ca09

You would most likely spend less money on one you build, though.

Many of the dow key relays on E bay are lower voltage or DC activated coils.
Perhaps others on the board might have a better source.

You could also feed your switched AC output to a small transformer to come up with the voltage you need....your choice.

Pete


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 6:04 pm 
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Joined: Sep Sat 06, 2008 6:17 pm
Posts: 1167
Location: Central Pa, 17044
Thanks guys, Pete, that's a nice youtube video you made.
I found one of them little cube type relays with a 12vdc coil
I used this same coil on a linear amp project and it seemed to carry the RF just fine.
By the way, the linear amp I had to part out...Just to many problems :(
But thanks again for your ideas!
Gary


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 Post subject: Re: Antenna Switch
PostPosted: Jun Tue 09, 2015 7:07 pm 
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Gary,

You need a relay with a 110/120VAC coil for the DX-60 unless you build a 12V DC supply powered by its switched supply which is an unneeded complication. The DX-60 is set up to conveniently supply 120VAC from its connector when in the transmit position. 120VAC coil relays are very common.

The tube type "electronic" T/R switches are very nice for full break-in CW use and will work for you. In the old days when TVI (television interference) was a concern you had to be careful using them because in normal operation they will tend to generate harmonic output from the transmitter but in most cases this is no longer a concern. The Johnson electronic T/R switch also doubles as a coffee warmer :) It gets rather warm. As noted you will still need an additional relay controlled by your DX60 unless you mute the R-1000 manually which is a pain.

I reiterate be careful buying used Dow Key relays. The minimal failure mode is a dirty contact, often only impacting the receive side, and it can be cleaned and I have had to do this with several Dow Key relays. A coil failure is a bit more expensive but it can be replaced. I have heard of more than one failing and allowing the transmitter RF directly into the receiver which would be extremely destructive to your solid state R-1000. I presume this comes from the N/C receiver contact becoming stuck to the common and pulled over to or close enough to the N/O contact but fortunately this hasn't happened to one of mine so I have never done an autopsy. One of the guys I talk with a lot burned a RF coil input winding in his 75A4 when this happened and the same failure in most solid state receivers would likely create a lot more damage than a burned coil. This is one of the reasons I like using an extra set of contacts on a cube relay to short the receiver input during transmit.

Final note, I have a Kenwood R-1000 but have never used it with a transmitter. According to my quick read of the manual it mutes by biasing off the RF amp and there MIGHT be enough RF leakage in your T/R switch to allow the R-1000 to reproduce your transmit signal and create feedback. A more common muting circuit in later equipment uses the AGC bus or similar to bias off all gain controlled stages which easily supplies sufficient muting but I have a feeling just shutting down one stage in the R-1000 may not be sufficient if there is any significant leakage in the T/R switch.

Rodger WQ9E


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 Post subject: Re: Antenna Switch
PostPosted: Jun Wed 10, 2015 4:07 am 
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I used Dow relays long long ago, but they didn't seem to work well long term. I bought a couple Viking T/R switches, and still use them today. I follow the receive output port with a mini-circuits distribution amp and splitter for all the receivers.

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