#341 

Great job explaining some commonly asked question Alan, thanks for taking the time to do so!

World-class exposition. Well done!

Have only recently stumbled across your channel, and I get valuable information with each new video I view. Thanks for the effort!

Very detailed and clear as always. Thank you for the great videos.

Love seeing the Nano used for things other than antenna tuning. It inspires me to use mine for other things. Thanks and 73s!

Awesome as always! Timely for me, too. I realized the other week that the local AM broadcast station is putting about +20 dBm into my rig (at the end of a long run of coax) when I use my 80m EFHW. I knew it was swamping the radio but hadn't thought much about it damaging things! Back to the AM broadcast filter build with me (for which I've been your fast pulse generator that I built the other day). I'm lucky to be a ham in the modern era where things like the NanoVNA and TinySA are available and when great education like this is available on demand on RU-vid. Thanks as always for your amazing explanations, W2AEW! 73 de AB4EN.

Another 'light bulb' learning moment for me! Alan, thank you so much for doing this demonstration. I always wondered about the bleed over. It also answers so many questions concerning these antenna switches for multiple radio hook ups to one antenna.

Great timing. Just sold our old QTH and moved into a new temp one here in NH. For the first time ever, I built a window pass through with three UHF bulkhead connectors so I can play with a few antennas without just running coax through the window. I also wanted to swap other rigs into an antenna and have my first 2 position switch. I never thought about the isolation ratings.

Would love to see a disassembly of such a thing, assuming the switch is different from a normal DC/AC/Audio switch to keep capacitive coupling down. Note how nobody have questions to what you actually showed us, because that is as always clear 😃

Always a pleasure. Thanks Alan!

Excellent demostration. Thanks for sharing.

Thanks for this. I've always wondered what I can do, now I can test my switch to be sure its safe!

I have two of the same switches. (4 ports) I like the isolation on them. Great video!

Very nice video, great topic, would love more on this. 👍👍

Your my favorite ham radio RU-vid channel.

An excellent video once again, I must admit I have never checked the isolation.

Thank you for the clear explanation!

Great presentation! Thanks for the information. I'm going to go test all my coax switches :-)

I have an older MFJ switch, that looks perfect on the outside. I was receiving cross-talk between the two antenna positions. Upon disassembly,I found the guts of the switch covered with a fine oily substance. Removing he oil and abrading the electrical "ground" surfaces inside the switch repaired the problem. I don't have a VNA, but I estimate that the isolation improved by almost 40 dB.

Excellent video! Just quickly tested my MFJ-1700c with my vna and got between 81 db (@ 1MHz) to 59 db (@ 150 MHz). The specs claim more than 60 db between 1.8 and 30 MHz. Internal construction is pretty decent for MFJ. I guess maybe I should do a video on measuring it on the MFJ-1700c and showing it's internals...

Excellent thank you much I used the same alpha Delta switches you do

Alpha Delta switches are well built and reliable. My shack has four. Thank you for showing us their performance.

Thanks! Simple, useful and interesting as always)

Execelent video, as always. Thanks!

Fantastic tutorial. Just what I needed. 73, Mark WU6R

Glad i found this video!

Alan, fantastic video and explanation. Your efforts are greatly appreciated! Dad used switches similarly as I remember, but they were round ones, either old B&W or some home brew ones. This was in the 70s-90's. I've been using 2 Alpha Delta 4 position switches, one to select between radios at the desk and one between antennas at the window. This setup has worked well. I am reconfiguring the window switch to select between UHF/VHF antennas, as I will shortly have only one HF feed line out to a remote switch (MFJ) at the tower. Just a thought....testing a remote switch's isolation would be a great "next episode" for you! 73 stay safe. de Cliff W3KKO

Excellent thank you so much for doing this work .

I've disassembled the blue MFJ-1702 low cost switch because of an intermittent connection; it's not great. You are better off purchasing the higher cost antenna switch such as the MFJ-2702. Thanks for the video Alan. 73s KN4JWZ

Great explanation. Thanks.

Thank you for sharing, I have to thought of using a nano VNA to test my switches. Yes you should look at your specs of your switches to know your bandwidth of your switch.

A great content, Alan! I really enjoyed watching this Video. Thx for sharing your experiences with us. Happy monday from SW-Germany & 73's de Your Friend Uncle Guenter

Hi always great info here, thanks.

So helpful as I enter the world of a coax switches

Thanks for the upload! :)

Great video, thankyou.

Thanks for another great video. My experience is that things get worse when devices and/or antennas are not properly terminated (bad SWR)

Good class.

Nice test of the switch for those working DC to daylight or Hf to 440. It's tought to find a switch that works that high to test.

As per normal..... 'no nonsence' & 'to the point' . Experiece really shows & makes it effertless . Thanks

Thanks Alan. Always thankful for your teaching. We never stop learning. I have wondered about just how much isolation there is on these switches. Wondering also what happens if someone has a high SWR on the common antenna port and if the isolation is still good with higher RF voltages due to the miss match. Thanks, Terry, WA0DTH

Thank you. That was educating. I will go with the alpha delta. Not good to "punch holes in the envelope ." N0QFT

thank you!

Thanks for a very well researched and presented video It's something I've been concerned with for some time but not had the opportunity to research in detail . I stopped using switches and reverted to a patch system after a switch destroyed the front ends of two QRP radios. The cause appears to have been poor earthing of the unused port when the switches wear in constant use . - The switches being of the type you refer to as the MFJ but come in various brands. Would be interesting to see an internal comparison of the construction between various switches . Richard G3UGF

Very nice video Alan, thanks a lot. 73s Pasquale IW0HEX

Nice video, thank you :)

Good Job..

Hello Sir, I love your videos on NanoVNA, they are very informative, however I couldn't find a video where you test the coil antenna. How could we correctly calibrate and measure a loop antenna with wireless single loop hooked up on channel 0? It would be really helpful

I've actually often wondered about this question - usually these are used to switch one radio between 2 antennas... I've wanted to have 2 radios connected to 1 antenna and I've been concerned about transmitting 100w (or more) directly into my other radio through a bad switch.

Hi Alan, How timely. I want to be able to switch between my FT450 and a Flex 1500 into my antenna system that uses an Ameritron RCS-8V remote switch. You have shown it can be easily done with a manual coax switch. Think I will go with the Alpha Delta for the added protection. You and the family stay safe. 73 WJ3U

At HF frequencies, it always amazes me what can be "gotten away with". At VHF, we have to start playing by the rules, and then up at UHF, everything has to be pretty spot on, otherwise it simply won't work. I have access to some pretty frightening test gear at work - I'll have to do some similar tests with coax switches up at UHF and se how it compares to the commercial combiners we use.

I've been wondering if my Alpha Delta can be reversed. No more switching coax for me. Thanks a ton

just lovely

Thank you, Thank you, Thank you

Just finding this video now, interesting, I've just purchased a remote control switch MFJ-4712 from DX Engineering, but my purpose is to run a Transmitter capable of 1 KW into one port and a receiver into the other port with the common port to the one antenna. I hope the isolation will be good enough can't find any spec for that so I'll have to do similar tests...good video thanks indeed. Clint - VK3CSJ

Great video as always - Thank you! “The unused port is grounded” Very curious to know how you ground your station from the second story operating location.

Yet another great video presentation! Thank you for generosity sharing. btw - How does the LibraVNa compare to the Nano? And… Have you ever seen/used the “Mini-1300” antenna analyzer? Thanks!

Would there be any more isolation between ports that are not adjacent to each other? Example: more isolation between ports 1 & 4 vs. between 1 & 2?

Any thoughts on Veritasium's latest video on propagation of electrical power in circuitry? It seems the internet is confused about transmission line theory.

Everything i read says UHF connectors(PL-259, SO-239) are antiquated and not suitable for modern VHF and up radios, yet almost every VHF/UHF HAM radio sold in the states today has an SO-239 output. Is it worth changing these out for a good quality BNC/TNC/SMA/N-Type connector? Can you do a video with some real world comparison between these coax connectors? love the videos, thanks

Some years ago you did a video about the RF Milivoltmeter Boonton. I bought a model Boonton 92B with the original RF probe (same S/N). But the probe cable need to be soldered again. Do you believe that if a small wire lenght (in the probe cable) were cutted off and a new soldering were done in the plug, this action could change the factory values?

@w2aew Alan, could you do a video how to property measure power output of a radio? Imagine you were getting ready to sell an Icom or Yaesu, and wanted to verify the power output on all bands, or even if you just purchased one maybe. How would an average ham (eg not everyone has a bird 43) properly verify the radio is operating and putting out proper power on all bands?

Wish I saw this earlier. Just had a potentially expensive mistake. Was operating off my Yaesu FT-450D and wanted to switch to my Kenwood 520-S. I have my antenna feed like connected to a meter/dummy load combo which I then connect to the transceiver. I went a little to quickly and connected the end from the dummy load meter to the Kenwood - inadvertently connecting them together and proceeded to try to tune up the Kenwood finals- didn’t realize my mistake while trying to troubleshoot the plate reading until the FT450 started smoking. So far Kenwood seems ok, but not receiving anything on 20 meters through the Yaesu. A lot of QRM right now on the Kenwood so going to see if it is still dead reception after the bands clear up. Crossing my fingers.

Excellent video Alan. I've been hoping you'd do a video about this subject for awhile now. By the way, there was an article done in QST on this subject awhile back (QST March 2020, Page 36), testing the newer generation MFJ RF switch (MFJ-2703). Using a separate RF Generator and Spectrum Analyzer, depending on the HF frequency (range from 3 to 30mhz) the port isolation ranged from -79db to -129db. It would be interesting to know if your NANO device could confirm those isolation readings for this newer MFJ RF Switch in this article. KF4HR

My first ham radio when I got licensed in 2011 was a Kenwood TS-830S. Great radio I need to dust off and make some contacts. Love your videos! I'm new to simNEC and want to purchase an inexpensive with decent dynamic range (70 - 80 dB) up to 500MHz. Is the nanoVNA V2 plus4 worth the $299 on Tindie or are there any other reliable sources? Thx de NO5X

Oh man. Yagis pointed in every direction, take my money!

Allan, those sma cables look awsome. Where would I find a set. I really need to upgrade...

Just answered a question that popped up regarding my antenna management! I'm not sure I understand completely what " XdB of isolation" means, however. If you have 60dB of isolation between position one and position 2 and your reference is -73dB yet your signal is +2dB at what point in dB of the signal do you not have enough isolation? Immediately upon hitting -13dB things will start smoking? Or, is it more a rule of thumb that you're over taxing your circuitry as your xmitter signal rises though -13 and up? I still new at this. Sorry if this is a question with an obvious answer. Thanks again for a great educational video.

Is it possible in this setup to add a dummy load to the unused radio, in case it is inadvertently activated? It would seem that it would be prudent to do so.

Teardown to compare the two switches and what make one better?

Hi, where did you found the set on null action sma sma male to sma female (avoid to destroy thos on the v2plus4 vna) ?

Do you think there is any difference with the switch grounded to the station ground

Would you please clarify something? I understand that when you say the switch sends the unused port to ground that the it is sent to the chassis of the switch. Should that switch be sent to watch ground?

Do you run a ground strap to your switches?

Is there a diseqc switch type system for UHF/VHF?

Could someone dumb this down for me? I want to hook up my base gmrs radio and digital police scanner to one antenna. Can I use an alpha delta switch (2 port a&b) to switch back and forth between scanner and gmrs radio to use one at a time. I currently disconnect the antenna coax from back of radios and move it back and forth and it's a pain in the A. Not sure if it matters, the transmit radio is only 20 watts. Thank you in advance.

Hi Alan , so say if i had a 50w ssb Galaxy 2547 on antenna port 1 😢, and say an Apollo 40ch SSB cybernet radio on port 2 , going into a half wave vertical , if the antenna switch was switched to the GALAXY CH35ssb port 1, and say the Apollo was on CH20ssb , when I modulate on the Galaxy I get some slight swing on the Apollo's signal meter through the RF leakage , is this in line with your video ?. without getting into dbm too much . Much appreciated.

Where did you find the PL-259 termination?

Did you calibrate each port on the VNA separately?

Got be 550 will it be safe to run two radios three this got 520s. And ts 440

Very interesting what happens if you put 1 kw into it ?

Which vna model are you using here???

So does that mean the whole switch is only usable "in reverse"? I'd like to get a 4 way (not including input port) so I can have two antenna ports, one for transceiver, and one for my nanoVNA - would like to bake the nanoVNA into a small go-box.

How much worse does it get in the 70cm band? Is it still safe? Sorry, I’m a newbie. Just got my tech license a few weeks ago.

So I have a quick question about your video...... Is it still safer to turn off the power to the other radios or does it make no odds I'd they are on or off

I have more than one rig and when I use a antenna switch to select which radio I am going to use, I always modify the switch so when not in line it will not go to ground. It is inline at the radio point so 100w would be the max the switch will see. In most cases being I use an amp, my radios are set to 45w out max.

It's my understanding that S0 is -73dBm for frequencies under 30MHz. For frequencies above 30MHz, S0 is -93dBm. So does that imply the safe input voltage for frequencies above 30MHz is 0dBm, or 1 mW? Or, for frequencies over 30MHz, it safe to go 113 dB over S9?

Does this matter if the 2nd radio is off?

What, you want to _coax_ me into using that switch safely? *badum, tish*

How do I rig 2 antennas with one coax

Pardon my ignorance but if the rigs that aren't being used switched off do you even have to worry about it?

This is a good analysis of the problem and I agree with your conclusions. I wonder whether your 530 S meter circuit is accurate enough to be trusted. Have you checked the S meter readings from a calibrated signal generator at the levels involved. Ie. is S9+25 db = -73 dbm + 25 = -48 dbm actually indicating s9+25 on the meter? Most manuals I have looked at suggest calibrating the s9 position but the rest of the scale is an unknown and for some radios, quite imaginary in terms of accuracy! (Liked and Subscribed) 73 Andrew VK1DA

You had me until the end. Maybe I don't understand it, but when you keyed up the top radio, if the antenna switch was isolating X amount of dB, they why would the signal meter on the bottom radio go S9 +20? Shouldn't it stay close to nothing?

Depends on the switch., I fried an SDR trying to pick up the signal uaing a cheap switch, when using an unconnected port as a SDR input.,

👍🙏🙏🙏👍

1:10 Re: Max input +20dBm or 100mW or 1/10 of a watt. Some hams have damaged their FT-991A, blowing up R1005 which is 150-ohms and 1/10 watt. That they've damaged a resistor that is 1/10 watt, and conservation of energy, all this implies that they've exceeded the recommendation of Mr Sherwood and subjected their poor little radio to something above +20dBm.

Didn't understand a word! But that is my fault. I will work on it and try again!

Wait a sec...is that a Nintendo DS stylus you're using?

I've used both good and not so good switches and they all have problems with them. Much better to have dedicated antennas to rigs.

Alan Wolke, can it be convenient to leave your email address?