So I bought a new 5-BTV to replace the one I had installed on the ridgeline at my mountain property.  It tuned OK on 10 and 15, but not 20 and 40.

I think it might be a 4BTV with a resonator added, but there are no labels left on it.

Anyway the new one went together pretty easily, so I start tuning.

Gotta run the 10m section to shortest to get the whole band under 2 SWR.  No biggie, as I don't really plan on using 10m much up there, even the low loss hardline is still nearly 8dB of loss for that run.

Next start tuning the 15m section...OK, shorter...shorter...what the heck?  Suddenly the SWR jumps up bad.

Reset to defaults...still bad.

Puzzle...ponder...rant.

Oh, I wrapped the 'extra' wire that connects the SO connector to the radial plate around the post to prevent it getting tangled.

Cut the extra off and back to good looking curves.

I even got it tuned for the psk/JT section of 80 using the resonator.

Then, when I go to re-route the coax from the cabin to the 5-BTV, I find it gnawed in half about 50ft from the end.  This is the second time this has happened.  Stoopid possums/raccoons!

Anyway, just a reminder that there is no good reason for 'extra' wire anywhere in an antenna system, even in the connection to ground.


ETA
I will be rebuilding the older BTV for use as a 40/20 antenna at the primary QTH.  If I can't make that work well I am getting a MFJ-1793.

I'm not familiar with that antenna but here are a few things to try, assuming you followed the installation instructions:

Measure SWR with an inline SWR meter with at least 5 watts of power from the radio.

Change coax length.

Add an RF choke (1:1 "balun") to the coax near the antenna's feed point. A dozen of "snap on" RF choke rings may work too.

Just did a quick search. It appears to be a "high Q" antenna. Make sure there are no large conductive objects near the antenna. This should be mentioned in the manual.
Also, did you install any radials? How many and what length? Is the antenna elevated or ground mounted? If elevated, the radial's length is critical and there must be radials for each band. I'm sure the manual talks about this.

As far as critters go, I can't tell you what will work. Perhaps try to put the coax into a conduit or buy direct burial rated coax and put it in the ground.
I remember one of my university teachers telling us about rodent problems that some military installations were facing. Rats disabled very complex ICBM rocket systems by chewing the control wiring. Some counter measures were deployed such as poison. Several active duty personnel did rodent control as their primary responsibility. The teacher mentioned something about new formulations used in cable insulation to repel rodents. Perhaps a "direct burial" rated cable has that added to prevent the problems you are facing? I'm not 100% sure.  Perhaps someone knows more about this?

For my next invention..........Coax, made with cayenne pepper infused into the outer insulation.  A free pair of rubber gloves is included with every spool.

It works fine now.  The only reason for the post was to cover how important it is to NOT have any 'extra' wire, even if it is 'just' in the wire from the coax jacket to the radial plate.




The 800ft of cable *IS* a bit of loss.  I figure about 3dB on 40 and closer to 5dB on 20.  But it is *SO* quiet that it makes up for it.