I'm considering adding a BNC connector to my Yaesu VR-5000. What could go wrong...?

mayidunk

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I have a VR-5000 that I've really only ever used to listen to the HF, SW and MW bands until recently, when I've started to become interested in seeing how it performs at the higher frequency bands. However, I seem to have discovered a slight roadblock of sorts, in that the radio only provides an SO-239 antenna connector to receive those signals. While it does also provide a high impedance connector for long wire antennas, that connector is mainly for listening to bands below 30 mHz. That being the case, the SO-239 is the only game in town if I want to get to those higher bands!

If I'm not mistaken, the SO-239 and PL-259 connectors are considered to be less than useful above 100 mHz. That being the case, I'm considering adding a BNC female connector to the radio, wiring it to the existing SO-239's internal connections using either RG-174 or RG-316 coax. It would be wired in parallel with the SO-239, so as long as an antenna isn't connected to the existing input, impedance mismatch shouldn't be an issue for the new connector, since the SO-239 would just appear to be an open circuit. And, as far as how much of that coax would be needed to make the connection, I measured roughly 5 inches as the crow flies!

So, what do you guys think? Am I on the right track? Please recognize that I do not claim to know exactly what I'm doing here, because I don't. I used to work on stuff like this when I was in the Air Force 50 years ago, but that was then, and this is now. Even my soldering skills are gonna need some time in the woodshed before I start in on this. Nevertheless, I have a Weller soldering station with a good tip, and along with other tools, and a good multimeter, I should have enough to get the job done right. While on the surface this job may not appear to be that difficult, I just want to be sure that my thinking is correct, as there are always dragons waiting around to prove you wrong at every turn. Usually in a nasty sort of way!

While I may still be aware of many of the safety hazards involved with working on any radio gear, such as taking off all the rings and watches before diving in, keeping one hand in your pocket so you don't get bit by the nasty stuff, and using a grounding strap so I don't zap things, please do me a favor and let me know if I'm missing anything as regards not only keeping myself safe, but keeping the radio safe as well. I don't want to release the magic smoke before its time!

So, let me know what you think! Perhaps installing this connector can give the radio new life in its old age... as well as myself, in a manner of speaking!

Thanks in advance for your thoughtful input!
 

mmckenna

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You won't get shocked off 12 volts. Just unplug the radio before working on it. Good idea to take rings/jewelry off either way.

No, UHF connectors are less than ideal, but a lot of commercial LMR gear uses them up into the UHF band. They are essentially a shielded banana plug and got their "UHF" moniker when UHF meant something else than what it does now.

Honestly, I don't think you'll notice a difference in performance. But if you want to try it, go for it. I know I swapped the old "motorola" connectors out on older scanners, installing BNC connectors just to make life easier.

If it was me, I'd just remove the UHF connector all together. Install an N or BNC connector if you want to. I don't see any benefit in keeping both connectors. Plus, it'll keep you from having to drill a new hole in the chassis, and make it easy to switch back if you want.
 

mayidunk

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It appears that the 50 ohm BNC connectors are good from DC to around 4 gHz. I was not aware of that! I guess I'll just have to replace the old "UHF" connector with the BNC, and be done with it!

Thanks for the quick reply.
 

kb5udf

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I was gifted a pristine VR5000. My impression is that unless you live in a fairly rf sterile/quiet environment, your radio will benefit a lot more from filtering than from swapping out the chassis antenna connector. But done properly such a swap won’t hurt. enjoy the hobby.
 

mmckenna

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It appears that the 50 ohm BNC connectors are good from DC to around 4 gHz. I was not aware of that! I guess I'll just have to replace the old "UHF" connector with the BNC, and be done with it!

Thanks for the quick reply.

Finding a BNC connector that will fit in the same hole at the UHF connector may be a challenge. You may need to get crafty with some thin washers.

On the other hand, the outer diameter of a UHF connector is the same as an N connector, so that may make this a bit easier if you don't want to try to make the BNC fit.


 

G6FGO

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It appears that the 50 ohm BNC connectors are good from DC to around 4 gHz. I was not aware of that! I guess I'll just have to replace the old "UHF" connector with the BNC, and be done with it!

Thanks for the quick reply.

Frankly, the difference will only be seen on sensitive measuring equipment. If you REALLY want to change the connector, use an N type. I did that on my Icom 7100 and was surprised to find an N type socket which was a direct swap. It is going to be easier than a BNC regardless purely because they are similar sizes, a BNC is going to need a fiddly blanking plate and then cutting out.
 

mayidunk

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Frankly, the difference will only be seen on sensitive measuring equipment. If you REALLY want to change the connector, use an N type. I did that on my Icom 7100 and was surprised to find an N type socket which was a direct swap. It is going to be easier than a BNC regardless purely because they are similar sizes, a BNC is going to need a fiddly blanking plate and then cutting out.
You may have just saved me some work. I'll check it out using the RSPdx to see how the noise floor looks on up the spectrum. If it isn't really bad, then I'm gonna leave it be. "If it ain't broke, don't fix it" may well be the right call, in this case. Thanks!
 

mayidunk

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Finding a BNC connector that will fit in the same hole at the UHF connector may be a challenge. You may need to get crafty with some thin washers.

On the other hand, the outer diameter of a UHF connector is the same as an N connector, so that may make this a bit easier if you don't want to try to make the BNC fit.


Thanks for showing me about the N connector. If I decide to make the swap down the road, that form factor looks like it might just drop right in.
 

mmckenna

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Thanks for showing me about the N connector. If I decide to make the swap down the road, that form factor looks like it might just drop right in.

It should. But, yeah, I don't think you'll notice any difference. Just use an adapter if you need to connect something else.

N connectors will have more than enough performance for that radio. Very common connector type in the two way radio industry.
 

RFI-EMI-GUY

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It is crazy that Yaesu used a Bakelite SO239 for a radio spec'd into the many GHz range. They probably did so because a Type N female is so similar to an SO239 that many hobbyists try to mate a PL259 to the Type N and bugger up the center blades. Motorola used SO239/PL259 on early 800 MHz mobiles Mostar, Micor, Syntor X; and got away with it by using Teflon insulation. Otherwise there was predicted some absorption losses that would heat up under 30 watts of 800 MHz waves. If you search well, you may even find an SMA with a form factor that matches the holes already in the chassis.
 

G6FGO

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These were used for test equipment where the manufacturer wanted to offer different connector options. These may fit: Check dimensions...



View attachment 175278

SMA are not designed for regularly connecting and disconnecting though, they are not robust enough. I am sure I read somewhere that 100 cycles is a typical life expectancy.
 

N9JIG

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If many connection/disconnection cycles is anticipated then BNC would be your best choice, they are designed to do just that.
While an N connector provides a slightly superior result over a BNC, the BNC would be less troublesome over the years.
 

G7RUX

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Using the VR5000 myself I would suggest that you wouldn’t notice a change in performance at all from changing to a BNC input connector, not one bit.
What the VR5000 *definitely* benefits from is some filtering; I find a Band 2 (VHF FM broadcast band) notch filter to be invaluable, especially if you want to listen to VHF airband.
 

mayidunk

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Using the VR5000 myself I would suggest that you wouldn’t notice a change in performance at all from changing to a BNC input connector, not one bit.
What the VR5000 *definitely* benefits from is some filtering; I find a Band 2 (VHF FM broadcast band) notch filter to be invaluable, especially if you want to listen to VHF airband.
First, thanks to all of you for providing good advice, and pictures to go along with it!

As for the above quoted reply, I suspect that will likely be my experience as well, since it's being used for receiving and not for transmitting.

I'm noticing almost without exception, that videos, articles, and other comments I've read about the SO-239/PL-259 all relate to its suitability for transmitting above 300 (100...?) mHz, as VSWR would definitely be an issue with that impedance "hump" (I think I got that right... ). This is absolutely more important for people to know, as no one wants to risk their rig over something like that!

As I mentioned earlier, I'll check it out later as I'm awaiting a new wide-band antenna to use in the apartment, and while the mount for it is an NMO, it has a PL-259 on the end of its coax. So, it should be an easy enough task to plug it into the SDR as I already have an SO-239 to BNC adapter to hook it up. I'm guessing the impact might be nothing more than the noise floor picking up at some point past 100 mHz.

I also found an FM notch filter that I used to use back in the day, so that will likely be put back into service, as well. Thanks for reminding me!

Anyway, thanks again for all the input. Happy New Year to all of you!
 
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W2JGA

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IMO, is it really worth the effort etc to swap out a connector for a dB or two? Especially on RCV?

I could see if we were discussing RG-8, 8X, LMR at the 100ft lengths,
 

G7RUX

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A couple of responses to the OP's reply above...

Firstly, the performance of the SO239/PL259 above HF does drop off but not in a way you would really notice unless you were going for DX receiving at UHF and above; the difference in performance at VHF and UHF is quite small. To be honest, the impedance of the receiver input itself probably varies far more than you might realise and would likely dwarf any mismatch from the choice of connector.

Secondly, receive and transmit performance is exactly the same, with the exception of power/voltage handling. This means that *if* you were to see a mismatch loss of 1 dB on Tx then you would also see that loss on receive. Again, 1 dB would be difficult to measure, let alone hear.

Finally, much is often made of small mismatches and the perceived risk of cooking the finals in a transmitter but the mismatch would have to be pretty spectacular to actually do that. Most units will cope with a 2:1 VSWR with no real issues and decent designs are protected against excessive mismatch causing damage.

To be honest, I would just pop a decent quality PL259 to BNC adaptor on the back of the set and forget about it...in fact, that is precisely what lives on the back of my VR5000. ;-)

PS: Here is the start of a series of pretty good posts about measurements and comparisons of different connector families which is well worth a read in this context.
 

ArloG

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Been watching this thread for a bit. I'm sorry. The only way (on my bench at least). An N-Type connector would be only way to upgrade.
Done once and forget it. At least for anything that works 30 MHz and above. That's how the 'big boys" do it.
SMA is fine. 500 connection cycles is the rated specs. A torque wrench is stressed. But who uses a torque wrench when tightening them. Right?!

Kind of strange that folks like Diamond will rate an antenna like the D130J up to 1300 MHz and put a SO-239 on it. Yeah. I looked it up.
Then, like the D3000N that I have. Uses N-Type. 30 MHz, "up to 400 MHz". VHF connectors invite iffy things for me at least.

I lived in Orlando Fl. Went to Skycraft Surplus a lot. So I have a box of N-Type connectors and various adapters, couplers. Amphenol, Pasternack, milspec, bagged and sealed stuff. They never ever let me down. Most are compression type and none have ever leaked.

Someone mentioned a dB or so.....not worth the fuss. Is for me. Just because. A dB or two is the difference in locking a signal on my C Band dish....or not.

Yeah. BNC is fine for test equipment, 'scope probes. HT's I guess. They still irk me for some reason.
Upgrading a radio connector? Use an N-Type and it will be the last one you ever need to crack the radio open for. Connector-wise anyhow. Pretty sure of that. And just don't skimp on cable. Ever. If it says 50 Ohm. Use it. Don't use 75 Ohm stuff. And never chinesuim junk.
The last danged thing I want to do when it gets down in the teens and way, wayyy below is mess with wire outside. Up a ladder, in the ice and snow. And wait for my fingers to wake back up inside and feel that tingle and burn. "Nope. Ain't the cable or connectors. Pretty sure of that".

2 cents. Forty-eight more and I can rap!.....nah!
 

W2JGA

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OP never mentioned where in the VHF/UHF/SHF bands he planned on monitoring, nor any mention if he was conducting EME.

Me thinks the OP just got mentally stuck on the idea that SO-239/PL-259 was of no use above 30MHZ.

I've seen plenty of business band UHF radios with PL-259 connectors transmitting 30+ watts.
 

prcguy

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Motorola uses PL-259/SO-239s through 500MHz on repeaters and duplexers so unless the OP is listening to 700MHz or higher stuff he won't notice any difference changing connectors. And if not done right he could make things worse.

I have Motorola 500MHz UHF duplexers here that have six SO-239/PL-259 connections in series between both the receiver and transmitter and these duplexers have about the same loss specs as other duplexers using N connectors. The Yaesu V-R5000 has one. I had a VR-5000 many years ago and would not spend any time or $$ swapping out the connector, its just not worth it on that receiver.
 
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