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Author Topic: 2x Radios, in tx how does one not kill the other?  (Read 437 times)

M7XAT

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2x Radios, in tx how does one not kill the other?
« on: January 12, 2023, 01:35:57 PM »

Hi Elmers. A question for you, if I may?
I got my licence only last year. Like most, I love to see shack photos with multi radios.
I’m lucky to own both a Yaesu FT-2000 and a new Kenwood TS-890s.

How do you transmit on one radio, without damaging the other? I do not have both switched on at the same time, when transmitting. I’ve got antennas for both radios.
I’ve heard that one has to be ‘switched to earth’… I’m not entirely sure how to do this (or even, what it means).
Can you tell me what I need to do, in a kind of ‘big dummies guide’ explanation?
Thank you.
Steve.
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W6MK

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #1 on: January 12, 2023, 02:13:28 PM »

Can you tell me what I need to do, in a kind of ‘big dummies guide’ explanation?

You've begun to think through the potential problems, which mostly have to do with keeping excess RF from your receiver sections.

Some people use antenna switches between their radios and their antenna feedlines. If you do this, you can use an antenna switch which grounds or otherwise adequately isolates unused switch positions. The amount of leakage between one transmitter and another receiver will then depend upon the isolation (usually stated in dB) from one position to another.

If you are using separate antennas for each radio, then the problem has to do with the transfer of RF from the TX to the RX antenna. This will depend on the frequencies, power level, types of antennas, etc.

When I am using separate antennas with separate radios, with antennas within half a wavelength of one another, I put a power limiting circuit in the feed line to the unused receiver. Such circuits are commercially available for about $50 or so. This requires using the radio's separate RX antenna connection.
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W1VT

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #2 on: January 12, 2023, 02:32:23 PM »

https://va6am.com/2017/02/04/so2r-numbers/
The SO2R general diagram below shows main sections of the SO2R setup. This is my preference shown on a diagram below with two radios, two computers and two amplifiers
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KA4WJA

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #3 on: January 12, 2023, 05:38:08 PM »

Steve,
1)  Your question comes up from time-to-time....and, while Zak, W1VT has give you a wonderful answer....if you're not interested in a full-on SO2R set-up?

The short answer (for a non SO2R set-up):
Then all you really need is a decent coax switch (to switch between your two radios), or if you have multiple antennas as well, then you'll probably want a second coax switch (to switch between your antennas)
Of course, if you've got the time/money and do want a full-on SO2R set-up, then look more at Zak's link.

I'm not clear on how many antennas you have, and what antennas they are...for what bands, etc...
Also, which radio are you using as primary (I assume the '890!!!)
The more info you can give, the better and more detailed the answers you'll get.  :)

Hi Elmers. A question for you, if I may?
I got my licence only last year. Like most, I love to see shack photos with multi radios.
I’m lucky to own both a Yaesu FT-2000 and a new Kenwood TS-890s.

How do you transmit on one radio, without damaging the other? I do not have both switched on at the same time, when transmitting. I’ve got antennas for both radios.
I’ve heard that one has to be ‘switched to earth’… I’m not entirely sure how to do this (or even, what it means).
Can you tell me what I need to do, in a kind of ‘big dummies guide’ explanation?
Thank you.
Steve.


2)  Before getting to the long answer...
Ironically, we just got through discussing how much signal one radio's receiver can handle from another radio's transmitter, when they are both connected to antennas that are separated by a certain distance....

And, fyi...most radios have their receiver connected to the antenna jack when powered off, so turning one radio off is not solving the issue...

The good news is that you can leave both radios on, while transmitting with one....you just need to either "isolate" the second radio (by using a coax switch, etc.)...or have it connected to an antenna a significant distance away from your transmitting antenna...

Have a look here at our recent discussion:
  https://www.eham.net/community/smf/index.php/topic,138012.msg1283234.html#msg1283234



Okay, now the long answer...
3)  If you just want a cheap, simple, and "easy-peasy" way to switch between your two radios (and antennas?), then I suggest a Daiwa CS-201a coax switch.  (and, a second one...to switch between two antennas if needed....or if you have 3 or 4 antennas, look for a Daiwa CS-401a)

You can find 'em here:
https://www.radioworld.co.uk/daiwa-cs-201a-2-way-1kw-coaxial-antenna-switch-with-so239-connectors

https://www.hamradiostore.co.uk/product/daiwa-cs-201a-2-way-1kw-co-axial-antenna-switch/

https://stecker-shop.net/CS-201a-DAIWA-Coax-switch

https://radioarena.co.uk/product/daiwa-cs-201a-2-way-coax-switch/

https://www.nevadaradio.co.uk/product/daiwa-cs-201a/


OR...if you want a Alpha Delta 2B switch (it's good...just that I personally prefer the Daiwa)
https://moonrakeronline.com/eu/alpha-delta-2b-coaxial-switch

https://www.radioworld.co.uk/second-hand-alpha-delta-2-way-coax-switch-500-mhz



4)  If you want to read about how others have gone about this...as well as isolation specs / tests of some of these...
Have a look here:

https://www.eham.net/community/smf/index.php/topic,132761.msg1217881.html#msg1217881

https://www.eham.net/community/smf/index.php/topic,132604.msg1217846.html#msg1217846

https://www.eham.net/community/smf/index.php/topic,136487.msg1265363.html#msg1265363

https://www.eham.net/community/smf/index.php/topic,136421.msg1264701.html#msg1264701

https://www.eham.net/community/smf/index.php/topic,135560.msg1254317.html#msg1254317


Here is a quote of mine, from one of those linked threads:
Quote
I've used this isolation to listen to / monitor my transmit signal on another radio...
Since I'd rather not subject the Daiwa switches to the Alpha 77Sx, I've generally just used them at 150 watts or less....but that still allows me to listen to my transmit signal to evaluate mic gains, etc. as well as key clicks, etc....

If you're interested in doing so....
Let's assume you have a typical HF rig with 100 watts out = +50dbm
Subtract the switch isolation (~ 80db) +50dbm - 80 = -30dbm
-30dbm is a strong receive signal, approx S-9 +43db, but should not "overload" any decent HF ham radio, so it is a great way to be able to "see"/"hear" all your spurious signals, whether IMD, key clicks, harmonics, etc....
(most HF ham rigs have a sensitivity in the -130dbm range, depending on rec bandwidth and what rec S/N is being used as the basis.....so, this allows you to hear and see any transmit spurs, and transmit noise radiated down to -100db from your carrier / PEP signal)

To be honest, I've never understood why all hams with two or more radios (that operate on the same bands), don't have 'em run thru an excellent switch....I know, I know, some swear by a "patch panel", and I won't argue these points here....but....
But, using a switch with a known isolation gives you another tool to use in maintaining your transmit signal as clean as possible, without spending much $$$.
(no, of course, this isn't a lab-grade test....and of course it won't "track you" as you move around the band, nor will you get a visual display as you do from a monitor scope, and no, this isn't a substitute for a spec analyzer.....but, if you have two rigs, my opinion is: do yourself the favor of using a good switch, and listen to your transmit signal on your other radio, especially listen off frequency / tune up and down 5 - 10khz, or even 20 - 50khz, and LISTEN to what you might be / or actually are transmitting, and make adjustments to assure your transmit signal is clean and intelligible!)



Steve, I hope this helps? 
If not....look at Zak's link again.  :)

73,
John,  KA4WJA
« Last Edit: January 12, 2023, 05:50:41 PM by KA4WJA »
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M7XAT

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #4 on: January 13, 2023, 12:32:04 AM »

Thank you all for the answers. I’m overwhelmed by the level of help and input, but that seems to be ‘the norm’ in the ham community, which I’m lucky to be a part of, thank you.
I’ll look and read through the links and try to digest it all.

To clarify on what I want to do..
I mainly use the 890, which has 2 antennas fed into it;
An end fed wire, which I use for 40/20/15m
A moxon for 10m.

I also want to use the Yaesu with a vertical for 10m (mounted on the same mast as the moxon) for local evening ragchewing, as some locals can barely hear me on horizontal polarisation, but mainly as a sub receiver, so i’ll be tx on the 890 on any band with the yaesu switched on.

Hope that helps.
Meanwhile, i’ll read through the links.
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KA4WJA

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #5 on: January 13, 2023, 08:45:41 AM »

Steve,
You're very welcome!
And, welcome to the wonderful world of the Amateur Radio Service!  :)

1)  Okay on all the new info...and, with this new info, you can probably skip a good deal of what's in the links I referenced earlier.
But, this discussion here will be important to your application...
https://www.eham.net/community/smf/index.php/topic,138012.msg1283234.html#msg1283234


2)  Again, if you have the time (and with a TS-890s, I assume you have a few extra pounds to spend), have a look at Zak's link for SO2R set-up.
 
To clarify on what I want to do..
I mainly use the 890, which has 2 antennas fed into it;
An end fed wire, which I use for 40/20/15m
A moxon for 10m.

I also want to use the Yaesu with a vertical for 10m (mounted on the same mast as the moxon) for local evening ragchewing, as some locals can barely hear me on horizontal polarisation, but mainly as a sub receiver, so i’ll be tx on the 890 on any band with the yaesu switched on.

3)  Unless you simply wish to unplug cabling all the time (and take the risks of forgetting something), then at the very least (if you don't wish to go all-in on a SO2R set-up), you will want to switch the 10m Moxon out-of circuit (and if it is real close, also the end-fed wire antenna), when you are transmitting with the FT-2000 on your 10m vertical (on the same mast as the Moxon)....and switch the 10m vertical out-of circuit when transmitting with the TS-890s on the Moxon (on the same mast as the vertical).

This can be done with a set of relays and switch circuit, controlled by the "transmit relay" contacts of both rigs, and you'll need to read the manuals (and schematics?) of your rigs and figure out the T/R timing/sequencing, etc.....BUT...
But, to be honest, my recommendation for you (especially since you're new to ham radio) is to go with Zak's original suggestions.

And, I'm a bit embarrassed that I wasted your time sorting through so much "stuff"....but the way your worded your original question I wasn't clear what set-up you had, nor what you wanted to do, and I made erroneous assumptions.  :(


So, Steve, while I do hope that I helped some....fact is, except for the one link I posted here in this message, you'll be better served following Zak's original recommendation!

73,
John,  KA4WJA
« Last Edit: January 13, 2023, 08:52:24 AM by KA4WJA »
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G4AON

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #6 on: January 14, 2023, 01:22:59 AM »

Steve, quite a few of us use an active antenna for general reception. They are very easy and cheap to make, although you can buy one if you aren’t into home construction.

An active antenna, particularly one based on the PA0RDT design, can be very inconspicuous and installed in the corner of a garden well away from house wiring and potential electrical noise.

A huge advantage of an active antenna is they can be wide band, covering from a few KHz to lower VHF. In some cases they receive better than a wire antenna, especially if your location is noisy. Another advantage is that you can knock off the supply Voltage to the antenna when you transmit, both protecting your receiver and your active antenna. The automatic switch just uses a single transistor, details on the PA0RDT page on my site.

I also have an article on a 4 way distribution amplifier for an active antenna that was published in the GQRP Club magazine Sprat.

https://www.qsl.net/g4aon/

73 Dave
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WA3SKN

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #7 on: January 15, 2023, 08:39:23 AM »

 kind of ‘big dummies guide’ explanation?...

Just about ALL the antenna switches out there now short the unused ports.
All you need do is put a short on the antenna input to the radio you are not using.  Any stray voltages induced are shorted to ground and will not damage the radio.
You have two radios and multiple antennas.  Put shorts on any antenna you are not using.  Put shorts on any transceiver antenna jack you are not using.  You might even do this with an antenna switch.

-Mike.
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M7XAT

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #8 on: January 15, 2023, 12:40:19 PM »

Again, amazed by the responses, nobody has wasted my time and I hope you think I haven’t wasted yours. I hope others will find this thread helpful in the future.
I’ll be looking towards the so2r solution.
Every day is a school day and just like a 1 watt bulb, I’m not too bright!
So each piece of advice makes look to google for what means what!
I have a ‘loop on the ground’ for RX, which works amazingly well on 40m, it’s a 15foot square and is pushed half an inch into the lawn. It’s a commercially made loop. I’m slowly learning and I have to switch off the radio to digest all that’s written.
‘Big dummies guide’.. i’m basically a technician licence operator in the UK, my passion for HF DX and radio, exceed my electrical/rf knowledge.
Thank you all.
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N8YX

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Re: 2x Radios, in tx how does one not kill the other?
« Reply #9 on: January 17, 2023, 10:32:44 AM »

Look into bandpass filters. Dunestar, DX Engineering and others sell them. They connect between your rig and antenna/amplifier; the multiband models support automatic band switching via control from the transceiver or via your PC and favorite contesting program.

If you want to take the human factor out of station operation with such filtering in place, there are a few ways to incorporate band lockouts. That is, one transceiver cannot be on the same band which another currently uses.

Physical separation between antennas resonant on the same band is also something to pay attention to, if you have sufficient space to work with. I'm currently putting together a multi-band/multi-op station, and my lot is approximately 300x700ft. An A-D DX LB-Plus (160-10M) dipole is rigged as a inverted vee in a tree about 100ft from an Imax 2000 (on my barn). If I run those antennas on two different radios, a 10M lockout and bandpass arrangement goes on both. In a tree around 150ft from the apex of the DX Ultra will be mounted a modified A-D DX-DD Plus, which will cover 60-30-17-12M...possibly 6M as well. This antenna will be dedicated to its own transceiver and probably won't use any sort of bandpass filtering, owing to distance and the resonant points themselves. Putting it at quadrature to the LB-Plus also minimizes near-field coupling.

Way out east of the house is a summer wildflower field that will be mowed then grow phased arrays for QRO 80-40-30-20M in the cooler months, and it'll also cover 11/12/17/60M in either omnidirectional or directional modes. It goes without saying that when this array is in operation, every connected rig in the lineup which mutually covers these bands gets bandpass filters.

A couple planned towers with HF yagis, logs and sloper arrays get the same treatment vis spacing of same-band resonances, shunting inactive feedlines and receiver protectors on every rig which can support the connection of such.
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