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Digital: Baofeng UV5R + External Antennas

Don Middleton (VA7IQ) on March 28, 2018
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I have been experimenting trying to figure out if it is even possible to use a Baofeng UV5R (super cheap) as an emergency email client on WinMor/RMSexpress.

I have it all set up with an external sound card product and it does work using the standard whip, a gain whip, or a simple 1/4 wave mag mount.

However, I have created 4 antennas so far (cubical quad, 3-el Yagi with simple dipole radiator, simple 19" vertical with 45-degree ground planes) and none of them will work with the HT. In fact, the HT cuts off PTT after 1/2 second or so for all of them. This weird behavior with electronic keying happens even into a dummy load with no audio cables to the sound card and a wealth of ferrites. It does not happen using a manual key in voice mode.

As I said earlier, the cables are covered in ferrites, I've even put foil around the sound card, put a huge commercial RF isolator for VHF on the feedline, and we've checked the signal levels with an oscilloscope. We know the sound card is not the source of the keying problem. It keys, the radio keys then dekeys, and the sound card is still keyed.

I am using SoundModem and DireWolf as the software TNC.

Now a curiosity -- if the jacket is disconnected from the coax, oddly enough the HT stays keyed. So, something on the coax ground is causing the Baofeng to dekey. It may be related to the way grounding works in that device, as the Mic and Spkr grounds are shorted to key the HT. I believe the antenna ground is tied directly to the speaker ground.

So my big question is, has anyone ever been able to get a Boafeng to run data into an external antenna other than a simple whip without ground plane?

There may be something simple and obvious that my buddies and I have missed so please share your wisdom.

If nothing else, in the last 2 weeks I've built more antennas than the last 10 years, so please don't beat me up for trying to get this cheap HT to behave.

Thanks Don M VA7IQ / AE7UP

Member Comments:
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Digital: Baofeng UV5R + External Antennas Reply
by KJ4DGE on March 28, 2018 Mail this to a friend!
Don,

No worries on getting beat up. Its good to see a HAM experiment and try new things. ITs what the hobby is all about. Not being familiar with the program you mention I can be of little help except to say the ground seems to be the culprit. Have you tried grounding the HT itself to a real ground rod of some sort?

It could even be reflected RF coming back down the coax to the radio perhaps. Keep us informed and if you get a solution let the rest of us know what the cure is.

73

Greg/KJ4DGE
 
Digital: Baofeng UV5R + External Antennas Reply
by NN4RH on March 28, 2018 Mail this to a friend!
Don't suppose you have an SWR meter or antenna analyzer ?
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by KG4RUL on March 28, 2018 Mail this to a friend!
Have you tried connecting the ground of the HT to an earth ground? You could make the ground connection by removing the antenna cable connector and slipping a suitably sized ring terminal, wired to an good earth ground, over the antenna jack. Secure the terminal by replacing the antenna cable connector.
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by W8QZ on March 28, 2018 Mail this to a friend!
I had a related (maybe) problem with one of those. In my case, I would key manually, the transmitter would cut off, and the whole radio would lock up. Required pulling the battery to reset. I gave up on it. My best guess was a bad battery pack - but I sold it really cheap at a swap (after describing the problem to the buyer), and got an Icom instead.

That UV-5R seemed like a 'flakey' piece of equipment, at best. Worth every dollar I paid for it, or maybe less ??

What you're doing ought to work - maybe getting some microsecond glitch in the keying line?

 
Digital: Baofeng UV5R + External Antennas Reply
by KB1GMX on March 28, 2018 Mail this to a friend!
I found that odd sounding so I hooked up my UV5R...

It worked normal. I tried a HB Jpole, Arrow OSJ146/440,
and a 4 element beam. Nothing weird.

Then I plugged in the programming cable hooked to the desktop. THings got weird like keying and intermittent operation and unwanted noises. Seems the programming interface has ground loop issues.

I then took the simple HB sound interface and hooked that up and it was normal. Why? ITs transformer Isolated and the transformers are also DC isolated (caps in series with audio leads).

FYI My RS HTX245 didn't like it and behaved the same
for both cases. I have two and one didn't like a common ground between the mic and speaker! One is a
19-1106 and the other a 1106A. Two radios not identical. My VX150 didn't like it either it wanted transformer isolation as well.

Obviously my UV5R (and three other HTs) doesn't like DC connections to the outside via speaker and mic jacks unless handled correctly and in an isolated form.

Why? without doing more detailed testing both radios use the "dual mic/speaker" connections for external hand mics with speakers. The hand mic is a two wire connection with the PTT in series. I believe that form of wiring is both RF sensitive and also sensitive to any DC leakage that puts the radio in TX state. With the right interface they all behaved well so its not fatal flaw.

So its either your interface or your doing something wrong. Its not the antenna unless the SWR is horrific. If that's true then you did something wrong to the antenna. Obviously a good antenna is not a problem. A test might be a dummy load and a common ground between the dummy load and the antenna. if that fails its likely not RF but ground loops.


Allison
 
Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on March 28, 2018 Mail this to a friend!
Thanks for all the responses.

I use a YouKits antenna analyzer and a Bird 43 SWR meter, and the antennas check out some.

My "sound card" module to USB has proper isolation transformers.

Works great with a whip (no ground) but not into a variety of antennas where the ground is connected.

But, the problem doe not occur using a speaker Mike, but only with a digital cable doing keying. The programming cable issues shared hint strongly at the problem.

It may well be a ground loop because to key requires shorting Mike and earphone grounds, so some differential must exist.

I will follow up testing with an MFJ antenna with ground plan, and will check connecting to yo a proper "ground".

Thanks thus far! Another step forward? :-)

Don
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by W1RKW on March 28, 2018 Mail this to a friend!
I vote for ground loop.
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by KB1GMX on March 29, 2018 Mail this to a friend!
Be careful of your system.

IN one case I had the transformers had a common ground
between them on the radio side and the RS radio had issues with that (noises on RX).

When I say isolated I mean the speaker leads have NO DC connection to the mic leads in any part of the circuit. Not even a commom ground at the mic jacks.

Also the UV5R transmits when there is a path from Mic audio hot to its respective ground, least mine does.
It will also transmit if the mic ground and the speaker ground are made common (it was a broken jack causing that). So wiring is important but it may not be RF.

Allison
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VE3CNU on March 29, 2018 Mail this to a friend!
I agree, it sounds like reflected RF coming back down the coax to the radio
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by W1RKW on March 29, 2018 Mail this to a friend!
Don,
I'm going to make an assumption here so correct me if I'm wrong. Your external sound card is USB and connected to a PC? If so, try this, break the ground connection to the PC at the AC mains.
 
Digital: Baofeng UV5R + External Antennas Reply
by K3FHP on March 29, 2018 Mail this to a friend!
Check the suggested spkr-mic wiring. These are standard wiring between Baofeng, Icom(some models) and Kenwood HTs. They use a resistor in the mic keying line. Check the net, lots of examples.
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by KC3HMS on March 30, 2018 Mail this to a friend!
The Baofeng units have a common ground between the antenna and the belt-clip screw that is on the antenna side of the unit. It's commonly used as a mount point for a Counterpoise. You should make sure this exposed screw is insulated and not grounding out if you have a different placement of the unit during your external antenna operations.
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by N6JSX on March 31, 2018 Mail this to a friend!
I've seen/had similar issues.

1. Using a TV-Twin J, I got RF back down the coax shield whacking the VSWR, badly. Solution, add a Bazooka/sleeve balun (really a 1/4wave RF choke) to the tap end of the coax making the coax function properly again and stabilizing the VSWR. Nice about a J is no ground plane required!!! Oh Quad/Quagi can have this same RF down the shield problem - use a Bazooka to climate that issue allowing the coax to perform as intended!

2. Ground-loop at the mic/PTT, as I had with my ICOM 2AT/IC-38 since the PTT is not a hard fixed switch. Solution, isolate the mic/spker and PTT from HT to sound card/PC. I purchased super small 1:1 isolation transformers for the speaker/mic lines. Not long ago I found good deals of surplus mini-transformers (10 for $5) at either Electronic Goldmine or MPJA. The PTT I used a simple-cheap Opto-isolator/Opto-Coupler chip.

A very quick Web search and I found this: http://www.wm7d.net/hamradio/ft920/picts/psk31_ft920.gif

This solved all my problems doing HT Packet/PSK31.
 
Digital: Baofeng UV5R + External Antennas Reply
by KD6VXI on April 1, 2018 Mail this to a friend!
Use 2 to 5 uF coupling caps in ALL audio leads.

Use opto isolators to key the radio.

Ground (earth) , b- and negative are all different. Your radio isn't behaving having them all tied together.

Higher quality radios take this into account. The cheap companies don't care. They just provided an upgrade path for you to purchase one of their digital radio offerings.

Which has isolated input, output and keying.

--Shane
KD6VXI

 
Digital: Baofeng UV5R + External Antennas Reply
by W8LGZ on April 3, 2018 Mail this to a friend!
Why is this a front page Article instead of being in the Elmers, Mods & Repairs, or VHF/UHF Forum where it belongs???????

Jim - W8LGZ
 
Digital: Baofeng UV5R + External Antennas Reply
by K1EHZ on April 9, 2018 Mail this to a friend!
You may know this already, but I'll just mention what I learned using the UV-5R. I use it routinely with fldigi.

The mic ground and headphone ground are isolated because they are the ptt circuit. So anytime they are connected, internally or externally, transmit is keyed.

I have a home brew computer interface with isolation transformers on both circuits. The transformer grounds are isolated on the radio side. The grounds can be connected together on the computer side because they are common when plugged into the computer anyway.

The UV-5R VOX must be turned on in the menu. The sound from fldigi then keys the radio.

I use whips and magmounts without any problems. I also have a 19" counterpoise connected to a belt clip screw which is common to chassis ground. A lot of RF flows in the counterpoised as measured with an RF current meter. Not sure where the RF goes without a counterpoise . into my hand and arm??

SMA connectors are fragile and I am told by a pro that they have a limited number of on-off cycles. Maybe the SMA is a bit flakey or doesn't like whatever adapter you are using.

Not sure this helps at all. From my perspective the cheap HTs are great for training on fldigi in class room situations and in regular operations. They also work well for unattended monitoring of digital messages which are auto saved in fldigi.

Jay
K1EHZ
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on April 14, 2018 Mail this to a friend!
Thank you for the suggestion of trying VOX.

I had earlier tried it and had determined on previous implementations that the VOX hang-time for the Baofeng is too long to allow Soundmodem (and probably others) to execute effectively.

Trying a new MFG-1754, this problem continues to manifest itself, while the radio performs very well in voice-only push-the-physical-key PTT mode.

The failure does not need RMSexpress/WinMor. It is quickly demonstrated using Calibration settings in the software modem program in Windows.

More testing to come....
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on April 14, 2018 Mail this to a friend!
Thank you. I didn't realize the screws for the clip and the lanyard loop were ground.

It would be nice if this would change behavior of the radio, but I suppose I've had them isolated/insulated thus far -- but it is surely worth watching out for.

Thank you.
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on April 14, 2018 Mail this to a friend!
I have also wondered about this being RF.

However, I have used 2 SWR meters (one a Bird) and an AA600 antenna analyzer to demonstrate that the SWR is very good -- 1.3::1 or less depending on the instrument.

To inhibit RF coming down, I also have a large RF Buxcomm VHF etc Isolator on the line, and it makes absolutely no difference.

Still trying the suggestions of those who have taken the time to share their wisdom.

Thank you! Don
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on April 14, 2018 Mail this to a friend!
Hi - great idea. I'm testing right now, and I am running the laptop on batteries. There is no ground other than on the lines interconnecting the laptop to the external sound modem.
Thanks! Don
 
RE: Digital: Baofeng UV5R + External Antennas Reply
by VA7IQ on April 14, 2018 Mail this to a friend!
To add more info, I am using the KF5INZ Easy Digi modem. It has opto-isolation for keying, audio lines both ways with isolation transformers, and .1UFD caps on the HI mike line. All these are recommended, and seemingly present.

A copy of the schematic is on the web at the following address. The lines to the computer on mine go into a USB interface integral to the product, but the rest is pretty much all the same.

http://www.giga.co.za/ocart/index.php?route=product/product&product_id=153
 
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