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

[mayidunk]

Again, a lot of discussion and referrals to articles that all seem to focus on transmission through a "UHF" connector. From what think I understand, there can be issues using this connector when transmitting through them at high power at frequencies higher then 30 MHz, which can lead to thermal issues at the connector, as well as high VSWR. However, how many dB would the same connection attenuate a received signal through the same connector at those higher frequencies? I've tried to find a simple graph showing this relationship, however all I can seem to find are fairly complex graphs that focus on transmitting through them.

Since this radio is capable of receiving up to 2.6 GHz, from everything I've read so far I can only imagine how much that 2.6 GHz received signal would be attenuated. Accordingly, such a signal might never even make it to the front-end of the radio! And, if that signal did make it past the "UHF" connector, the receiving antenna would likely to have needed to be right next to the transmission antenna in order for that to happen! Of course, I'm kidding...

In the end, It's apparent that that the SO-239/PL-259 connectors were designed during an era when 30 MHz was considered to be about the highest frequency that would likely be used by the majority of radio equipment of that era. As well, all of the test equipment that I remember using back when I worked on Tropospheric Scatter, long-haul radio systems, used BNC connectors. If memory serves, when line-of-sight microwave links came into use, wave guides, and rigid coax transmission lines replaced the flexible transmission lines used below 30MHz. I'm fairly certain that "UHF" connectors weren't even considered useful in these applications for any purpose. That all being said, it has been over 50 years since I worked on stuff like this, and since I haven't been at all immersed in the art over the ensuing years, I will defer to your knowlwdge and experience in these matters.

I'll just play around with it, and see what happens. If I were looking to do some serious UHF DX'ing, I would definitely be using a much better radio, and it would likely not have an old school "UHF" connector for its antenna input! However, not having thousands of dollars to spend on such equipment, I'll just play around with the VR-5000, and enjoy the discovery aspect of it. Besides, I really wasn't intent on making a silk purse out of this radio, it was just a pleasant diversion to occupy me. My dance card ain't as full as it used to be, and little projects like this help me to keep busy.

 

[G7RUX]

Again, a lot of discussion and referrals to articles that all seem to focus on transmission through a "UHF" connector. From what think I understand, there can be issues using this connector when transmitting through them at high power at frequencies higher then 30 MHz, which can lead to thermal issues at the connector, as well as high VSWR. However, how many dB would the same connection attenuate a received signal through the same connector at those higher frequencies? I've tried to find a simple graph showing this relationship, however all I can seem to find are fairly complex graphs that focus on transmitting through them.

Since this radio is capable of receiving up to 2.6 GHz, from everything I've read so far I can only imagine how much that 2.6 GHz received signal would be attenuated. Accordingly, such a signal might never even make it to the front-end of the radio! And, if that signal did make it past the "UHF" connector, the receiving antenna would likely to have needed to be right next to the transmission antenna in order for that to happen! Of course, I'm kidding...

In the end, It's apparent that that the SO-239/PL-259 connectors were designed during an era when 30 MHz was considered to be about the highest frequency that would likely be used by the majority of radio equipment of that era. As well, all of the test equipment that I remember using back when I worked on Tropospheric Scatter, long-haul radio systems, used BNC connectors. If memory serves, when line-of-sight microwave links came into use, wave guides, and rigid coax transmission lines replaced the flexible transmission lines used below 30MHz. I'm fairly certain that "UHF" connectors weren't even considered useful in these applications for any purpose. That all being said, it has been over 50 years since I worked on stuff like this, and since I haven't been at all immersed in the art over the ensuing years, I will defer to your knowlwdge and experience in these matters.

I'll just play around with it, and see what happens. If I were looking to do some serious UHF DX'ing, I would definitely be using a much better radio, and it would likely not have an old school "UHF" connector for its antenna input! However, not having thousands of dollars to spend on such equipment, I'll just play around with the VR-5000, and enjoy the discovery aspect of it. Besides, I really wasn't intent on making a silk purse out of this radio, it was just a pleasant diversion to occupy me. My dance card ain't as full as it used to be, and little projects like this help me to keep busy.

To reiterate what has been said before, the SO239 is perfectly fine and although it does have increased loss over other, more modern high-performance types this will not cause a noticeable issue for you.

Yes, the SO239 *can* introduce issues with heat if pushing significant power through it at high frequencies but this is not what you are trying to do here. That said, the (?)0.5 dB of attenuation you might see is still there for receiving but you'd have difficulty measuring this reliably, let alone notice it on a scanner.

The connector losses are, quite simply, dwarfed by other mismatch losses in the whole system, including by the mismatch seen in the actual front end of the wideband receiver.

One extra point to note is that for BNC, TNC and N-type connectors, the core of the connector structure is the same for all of these so their basic performance is very similar.

My VR5000 has a 90-degree PL-259-to-BNC-socket adaptor on the back of it since it turns the cable in a convenient direction and BNC performs perfectly well for me, that being what's on most of my small patch leads.

 

[mayidunk]

To reiterate what has been said before, the SO239 is perfectly fine and although it does have increased loss over other, more modern high-performance types this will not cause a noticeable issue for you.

Yes, the SO239 *can* introduce issues with heat if pushing significant power through it at high frequencies but this is not what you are trying to do here. That said, the (?)0.5 dB of attenuation you might see is still there for receiving but you'd have difficulty measuring this reliably, let alone notice it on a scanner.

The connector losses are, quite simply, dwarfed by other mismatch losses in the whole system, including by the mismatch seen in the actual front end of the wideband receiver.

One extra point to note is that for BNC, TNC and N-type connectors, the core of the connector structure is the same for all of these so their basic performance is very similar.

My VR5000 has a 90-degree PL-259-to-BNC-socket adaptor on the back of it since it turns the cable in a convenient direction and BNC performs perfectly well for me, that being what's on most of my small patch leads.

I totally agree with you. Like I said earlier, I'm just going to play with it/use it as is. I'm not going to try to "fix" anything at this point because I now realize that there's really nothing to fix. No sense risking a good radio because of a loss in S/N that I'm not even going to notice.

However, out of curiosity I'm still going to hook the new antenna up to the RSPdx just to get an idea of what it can see up to ~2 GHz. While the SDR can show me a sweep of what the antenna is picking up, I won't be able to do much more than look at what the noise floor is, and how many dB up from there the signals peak. And while without context it won't really tell me much else, it might still give me a clue initially as to how the antenna itself will perform. That is, if there's even anything around here for it to see that high up!

 

[ArloG]

I got a bit curious of actual frequency sweep data of the x259 connector and got sidelined.
Haha. I'll be a-chickin'-lickin. Something I always knew was the SO259 could have a banana pin connector shoved in it.
In the day when coax was being introduce to amateur radio buffs. Adding a threaded shielding ring and using coax killed the chance of getting RF burn and added antenna stability. And 'stuff'.
Fine. And cool.

What I did not know was. If you remove the outer bayonet ring from a BNC. You can stick the remaining plug right in an N-Type socket.
And that design was engineered in.
Way more cooler. Dang!

 

[G7RUX]

I got a bit curious of actual frequency sweep data of the x259 connector and got sidelined.
Haha. I'll be a-chickin'-lickin. Something I always knew was the SO259 could have a banana pin connector shoved in it.
In the day when coax was being introduce to amateur radio buffs. Adding a threaded shielding ring and using coax killed the chance of getting RF burn and added antenna stability. And 'stuff'.
Fine. And cool.

What I did not know was. If you remove the outer bayonet ring from a BNC. You can stick the remaining plug right in an N-Type socket.
And that design was engineered in.
Way more cooler. Dang!

Additionally, you can push a N-plug onto a BNC socket and it makes decent contact.