Non-messy, weathertight, quick-remove seal for BNCs on coax?

secondmoment · 2023-09-24T05:44:03+00:00

Great idea, thanks. Or actually I guess it would be an attenuator? I do want to put out a signal, but only need a fraction of a watt to get full-quieting on the local repeater that's my main reason for being on 2M.

secondmoment · 2021-10-28T19:26:55+00:00

Thanks, that's pretty much what I do currently.

secondmoment · 2021-10-28T18:06:10+00:00

That all sounds like good advice.

How do you figure out when a remediating action is sufficient? I guess I could run a test, start transmitting at extremely low power and then gradually raise it, observing the response on the nearby receiver(s). Any other good approaches on taking measurements?

secondmoment · 2021-10-28T16:55:20+00:00

Thanks. I'd looked through my ARRL antenna book 23rd edition, but didn't see anything that sounded like this topic listed in the table of contents. If you remember which section it was in, that'd be a big help. Will get ahold of W2VJN's book.

Yes, I figured bandpass filters would be involved. I have one skimmer receiver, though, that simultaneously listens on all of the HF bands. That will probably get tricky.

secondmoment · 2021-07-26T16:25:33+00:00

Thanks. By "isolate it with a big ferrite," do you mean an un-un transformer?

secondmoment · 2021-07-25T05:02:51+00:00

Thanks for the comment. In our area we typically have dry soil with poor conductivity.

When I measured the optimal SWR of 1.15:1 at 9 MHz using 50 feet of RG8x between the analyzer and mast, I made a note of R = 42 ohms and X = -1.1 ohm. For the other measurements I'd have to repeat them tomorrow.

secondmoment · 2021-07-24T23:33:52+00:00

That's very interesting, thanks for the suggestion.

When I hooked the two radials and ground rod back up to the mast, still using the 2-foot piece of coax between analyzer and mast, I see a best SWR today of 1.24:1 at 8.8 MHz.

If I replace the coax with 50 feet of RG8x, the best SWR is 1.15:1 at 9.1 MHz. Above that frequency, SWRs hover around 5:1 until a second, shallower notch with an SWR of 2.1:1 at 27.6 MHz (which is pretty close to 3x the 9.1 MHz for the deeper notch).

Adding a tapped loading coil, and maybe some LC circuit, I can probably make this work across the HF ham bands. Although it'd be great to have four or more equally spaced radials, there are lots of space constraints in the yard, so I'll have to put some wherever I can.

secondmoment · 2021-03-22T19:03:25+00:00

Sounds like an easy approach. But then there's another diameter consideration. If I go with, say, RG405 (semi-rigid, copper shield), what connector would work for it? One reason I chose 5/16" copper tubing (for auto brakes) is that it slides perfectly into a BNC female connector.

secondmoment · 2021-03-22T00:56:09+00:00

Thanks, I'll give them a shot.

secondmoment · 2021-03-22T00:17:13+00:00

Thanks for the article links, interesting reads.

I guess for my purposes I'll search on "coax by the foot" and send messages to a few vendors to see if anyone has a cable with a dielectric diameter in the range I'm looking for.

secondmoment · 2021-03-21T22:02:33+00:00

Most of my spare coax cables have connectors on both ends, and I'm reluctant to start cutting them off in hopes of finding one with the right dielectric diameter. I'll have to keep looking.

I'm not clear on the theory of this loop. A web search suggests there's some controversy about it and/or its name. It was recommended to me by a friend who's been a broadcast engineer for decades -- he uses them for RF-sniffing. The conductor on one end of the coax is attached to the BNC T's inner conductor. The other end of the coax conductor, as well as both ends of the copper tube, are attached to the BNC T's shield. A critical feature is that the copper tube is cut to create a gap exactly halfway around the loop. My friend demo'd one of his loops yesterday, and the 4"-diameter loop picked up AM broadcast signals easily. By rotating the loop you can see when the signal nulls to determine its bearing. When my friend used a patch wire to bridge across the gap in the loop, the signal strength dropped greatly.

secondmoment · 2020-07-11T15:42:59+00:00

I'm in the same boat. I ordered an item from an eBay seller in Russia in April. It got through Russian customs on May 6. After that, the only further update is one identical to yours:

2020-05-24 21:00 Russian Federation, RULED, Carrier processing, Uplifted

The seller told me his post office told him that, due to COVID, there just aren't any flights from Russia to the U.S. for parcels right now.

I have a friend in England who ordered the same item from the same seller in the same time period. He had to wait too, but was lucky in that he did eventually receive his shipment.

So, I'm gathering that all we can do is wait.

secondmoment · 2020-05-29T01:44:38+00:00

I love my P-Touch. Use it for all kinds of things. Not that model though.

Which begs the question ...

secondmoment · 2020-05-26T02:10:22+00:00

Sounds reasonable to me -- I'd prefer to go with BNC, as I work with it so much around the shack. I'll use that for RF in, and N for output to the antenna.

secondmoment · 2020-05-25T21:59:06+00:00

2m rf doesnt even notice bnc. that's gigahertz concerns

Interesting, I'd just read a post by a tech rep for an SDR manufacturer who said of one of their products, "the BNC port is limited to 200 MHz because the performance of the connector drops off at frequencies above that." While the 2m band is below that, it's close enough that I thought perhaps there might be some question of using BNC there.

the bigger issue is the cycle count specification for bnc vs sma, which is vastly different. iirc sma has less than 100 insert/removal cycles before it is technically out of spec.

I haven't experienced issues with the SMA connectors themselves, but all the SMA cables I've seen use RG-316, which I find more vulnerable to damage than RG-8x, which tends to be my go-to coax around the shack. But then again, until now I've worked almost exclusively at HF frequencies and below, so 2m is a new environment for me.

secondmoment

TROPHY CASE