Low Profile VHF Antenna Performance

[lb2910]

Since that is the LE tourpack, it will be interesting to see if you get any RFI from the circuitry. It would make sense that HD has that managed, since they know radio equipment will be used on/with the bike.

There shouldn't be any. Other than the LED brake/turn signal bar on the back, there is nothing else in the box. I use it as a trunk. There is a large metal plate covering the bottom of the box which might help a little with ground plate'ing along with the foil tape idea from MMCKENNA.. I'll post some un-scientific results and pics after the install...

 

[slowmover]

Suppliers like McMASTER-CARR sell foil in all sorts of metals and sizes and backings.

 

[west-pac]

Two more options to consider. There are VHF/UHF fold-over antennas in that 30-40 inch range. You simply pull up on the antenna, and fold it over. That would save you time and trouble from actually having to remove the antenna completely.

Another option is an antenna MOUNT that can be folded over.

Years ago I had an antenna unscrew itself and fall off my truck. By the time I realized it was gone I retraced my route and found it in the middle of an intersection. Unfortunately it had already been ran over and was no longer usable. My concern with mounting and dismounting the antenna everyday would be, at some point you may not get it as tight as needed, or the threads may loosen, and the antenna may fly off.

 

[west-pac]

Whoops, it appears in my haste, I only read one page of comments, instead of all 3 pages. I see we've moved on from antenna selection. Disregard my last comment. 🤣🤣

 

[lb2910]

Well.. the install did not go as planned.. HAHA.. First off, the thickness of my lid was more than I anticipated. So the 3/4 hole NMO mount (see attached pic) I got did not have enough space between the underside part and exterior round antenna connector. The end result was, when I threaded the outer ring onto the inner ring, it did not seat all the way. So when I threaded the whip antenna onto the NMO mount, the whip did not connect with the cable element in the center. YAY...

Second, the SMA female connector for the RG-58 cable crimp did not go well. I'll just leave it at that! 🤣 About the only thing that went well was the foil tape.

So... I am now ordering another NMO mount for thicker surfaces. I'll run that cable then go back to my original idea of a BNC connection and adapter. This will give me a quick release for the radio from the antenna. Never a dull day in my world!!!

 

[mmckenna]

So... I am now ordering another NMO mount for thicker surfaces. I'll run that cable then go back to my original idea of a BNC connection and adapter. This will give me a quick release for the radio from the antenna. Never a dull day in my world!!!

Yeah, we probably should have mentioned the 'thick mount' NMO's.

 

[lb2910]

Yeah, we probably should have mentioned the 'thick mount' NMO's.

All good... its a learning experience for me I assure you!!! It got too dark to snap some pics of the install by the time I got around to figuring out I couldn't make what I had work. I'll take some tomorrow and post. The foil idea was MONEY!!! Lot easier than going full on thin sheet metal. When I post the pics, you can tell me if my "quasi-ground plate" is functional. More to follow sports fans!!

 

[mmckenna]

All good... its a learning experience for me I assure you!!! It got too dark to snap some pics of the install by the time I got around to figuring out I couldn't make what I had work. I'll take some tomorrow and post. The foil idea was MONEY!!! Lot easier than going full on thin sheet metal. When I post the pics, you can tell me if my "quasi-ground plate" is functional. More to follow sports fans!!

Glad it worked.
Also glad you didn't try to force the incorrect NMO mount to work. Having the center contact not make a good connection would have lead to a lot of frustration. The thick mount will do what you need and be reliable.

Since you have the black shiny boxes, you can hit the antenna, coil and the gasket with some Armor all and shine it up. Will really make it look good.

 

[lb2910]

Well.. after waiting for the right parts and an unexpected out of town work trip thrown in for good measure, I FINALLY finished the install. I tested everything and the results were outstanding. I was getting MAJOR improvements with both Tx and Rx. Keep in mind the picture showing the actual radio was just to show how I did the BNC connector into the radio. The radio will go into the covered and zippered pouch right next to it for protection. The BNC connector will have a rubber cover that will protect it from water, debris, etc. Feel free to let me know if there are any improvements I can do. Thanks to all for the great help!! Especially MMCKENNA... YOU DA MAN!!!!

 

[mmckenna]

Looks good. Glad it's working out well.
Never underestimate the power of a good external antenna.
I really wish more hobbyists took this to heart.

 

[lb2910]

Looks good. Glad it's working out well.
Never underestimate the power of a good external antenna.
I really wish more hobbyists took this to heart.

Couldn't agree more about the external antenna.... MUCH better performance...
Regarding my quasi "ground plate"... anything else I can do to help performance? Or that about as good as it'll get given the parameters of the install?

 

[mmckenna]

Couldn't agree more about the external antenna.... MUCH better performance...
Regarding my quasi "ground plate"... anything else I can do to help performance? Or that about as good as it'll get given the parameters of the install?

My only concern is that the two pieces of tape are making a good electrical connection with the NMO base. Did you lay the tape down and then install the mount? I'd not want the adhesive in the way.


And, I noticed the crimp on the BNC looks a little oblong. Probably not a big impact, but if you replace it, make sure you are using the proper crimp tool. Should end with a nice even hexagon shape. Put some marine grade heat shrink over the crimp, too. Acts as a good strain relief.

 

[west-pac]

Wouldn't the adhesive

My only concern is that the two pieces of tape are making a good electrical connection with the NMO base. Did you lay the tape down and then install the mount? I'd not want the adhesive in the way.

I typed out a comment earlier today questioning that very thing; then deleted it all, as I thought I would've been over-complicating it.

I presume you could check continuity between the 2 strips of aluminum tape by using a VOM/DMM. I also think using a sheet of aluminum foil on the interior of the lid would provide a better ground plane than a strip or 2 of aluminum tape. It would be easy to adhere the foil temporarily with scotch tape, then poke the NMO mount thru it, reattach the antenna, and see if the signal strength has increased on the radio.

 

[lb2910]

My only concern is that the two pieces of tape are making a good electrical connection with the NMO base. Did you lay the tape down and then install the mount? I'd not want the adhesive in the way.


And, I noticed the crimp on the BNC looks a little oblong. Probably not a big impact, but if you replace it, make sure you are using the proper crimp tool. Should end with a nice even hexagon shape. Put some marine grade heat shrink over the crimp, too. Acts as a good strain relief.

So the foil tape should actually make contact with the NMO base? Because it definitely is. That said, yes.. there is obviously adhesive also making contact with the NMO base. Should I look into somehow stripping the adhesive where it contacts the NMO base?

And yup... the BNC crimp is straight up amateur hour.. I thought I got the right crimping tool and found out that it wasn't. So I took another ratchet crimp tool I had and crimped it with that. It's oblong but it does hold nicely. And there is nice heat shrink wrap over the crimp as well. It's not marine grade but its pretty thick.

 

[lb2910]

Wouldn't the adhesive

I typed out a comment earlier today questioning that very thing; then deleted it all, as I thought I would've been over-complicating it.

I presume you could check continuity between the 2 strips of aluminum tape by using a VOM/DMM. I also think using a sheet of aluminum foil on the interior of the lid would provide a better ground plane than a strip or 2 of aluminum tape. It would be easy to adhere the foil temporarily with scotch tape, then poke the NMO mount thru it, reattach the antenna, and see if the signal strength has increased on the radio.

I don't have a way to measure the signal strength. So I'd be going strictly on faith with that one. I think the foil tape did a decent enough job. When I tested the range, I was a several city blocks away and had both buildings and terrain in between both radios and the Tx/Rx was great. Between getting my radios aligned and tuned and the external antenna, I think I'm sitting pretty decent at this point.

 

[mmckenna]

So the foil tape should actually make contact with the NMO base? Because it definitely is. That said, yes.. there is obviously adhesive also making contact with the NMO base. Should I look into somehow stripping the adhesive where it contacts the NMO base?

The foil tape should have gone down first, then drill the hole and put the NMO mount through it. The foil should have been sandwiched between the NMO mount and the fiberglass.
I wouldn't worry about stripping the adhesive off, there's going to be some capacitive coupling like you'd get with a mag mount, even with the adhesive there.

 

[mmckenna]

And yup... the BNC crimp is straight up amateur hour.. I thought I got the right crimping tool and found out that it wasn't. So I took another ratchet crimp tool I had and crimped it with that. It's oblong but it does hold nicely. And there is nice heat shrink wrap over the crimp as well. It's not marine grade but its pretty thick.

No worries, if it works, it works.
If you ever want to fix it, take a cold six pack of beer by your closest radio shop around lunch time Friday and ask one of the techs to crimp it on for you.

 

[mmckenna]

I don't have a way to measure the signal strength. So I'd be going strictly on faith with that one. I think the foil tape did a decent enough job. When I tested the range, I was a several city blocks away and had both buildings and terrain in between both radios and the Tx/Rx was great. Between getting my radios aligned and tuned and the external antenna, I think I'm sitting pretty decent at this point.

You don't need a full 360º ground plane for it to work. Plenty of antennas out there with 3 ground radials at 120º spacing. You've got 4 short one, less than ideal, but better than none at all, and better than the antenna on top of the radio.

 

[lb2910]

You don't need a full 360º ground plane for it to work. Plenty of antennas out there with 3 ground radials at 120º spacing. You've got 4 short one, less than ideal, but better than none at all, and better than the antenna on top of the radio.

Based on your advice, I took the foil off and then reapplied it per your instructions. I covered the hole from the underside, then punched the NMO antenna contact part through the foil and threaded the top/outer mount. So now there is 100% contact with the base of the NMO mount and the foil. I put another layer on top of that layer just to protect the connection and to provide a bit more water resistance. Tested it again and works perfectly!!!

 

[mmckenna]

OK, good deal. Glad it's working well.