antenna glue

[w5omr]

Does anyone know what the electrical dielectric of Elmers 2-part Epoxy is?

Even before I dropped my bug catcher coil on a concrete parking lot and then repaired it, straightening the bent turns, then coated the joints where the wire meets the support rid with a few coatings of "Super Corona Dope", there were tell-tale signs of Zorching.

After I applied the corona dope to those junctions, I covered 'em with Elmers 2-part epoxy.  bug catcher still torches.

is there not enough insulative properties in Epoxy?:

[KL7OF]

You can use the kitchen microwave to test a cured glob of epoxy.......Determine its zorch factor easily...

[w5omr]

You can use the kitchen microwave to test a cured glob of epoxy.......Determine its zorch factor easily...

I think I thought of that, but while RF might be RF, materials subjected to RF in such tests react differently at frequencies as diverse as 4MHz and 1GHz.  The highest frequency I can generate in the truck, in the HF bands, is 29.7MHz, and I certainly don't have to worry about a Zorch on 10m, when the whole coil is by-passed and the length of the whip is a 1/4w on that frequency.

Two-part Elmer's Epoxy might react differently at 1GHz, but be perfectly 'ok' at something under 50MHz.

Conversely... (I get stone-walled when I debate myself...)

I know John/BXO learned about PVC the hard-way, by winding up a 75m coil on a form made of PVC... and while it was 'ok' for small-voltage testing, when the full B+ was applied, and RF Was being GENERATED (@ about 1kW DC input) then the plate current would rise, grid current would fall, you couldn't find the 'dip', and when he looked in the back of the rig, after the B+ was shut down, the coil was (to quote John) "all droopy-fied".  It fell apart under the presence of High RF Energy, at a relatively low frequency (3.9MHz)

So, is RF "RF" at any frequency, or do different materials react differently, depending on the frequency used for the test?

[KL7OF]

I don't know if "RF is RF at any frequency"  That's a tough one for me....I can tell you my experience however....I have used the microwave test on items like hot glue, pvc, lexan, acrylics etc that were to be used at HF ...some items pass and some don't  and I've had good luck with the materials that pass ....
    It is an interesting story about winding a 75m coil on PVC and having it get droopy-fied...I have used PVC for coil and plate choke forms with good results in high power transmitters....
     

[KM1H]

What is the voltage at the zorch point? You can calculate that by guestimating the electrical length of the antenna at that point and Id guess it is pretty high.

How about melting some polystyrene rod once you remove the moo goo?

Carl

[w5omr]

What is the voltage at the zorch point? You can calculate that by guestimating the electrical length of the antenna at that point and Id guess it is pretty high.

How about melting some polystyrene rod once you remove the moo goo?

Apparently, all I need to do, is keep the damn thing dry.  Last night, coming back to Houston from East of Shreveport, LA, I broke in with Grant/W4BVT and the Tron/WA1HLR and managed to carry on with those two from the Texas/LA state line until they signed.  John/KX5JT broke in about the time the Tron was signing and Timmy said "I hear John in there, but your signal was louder than his is!"   

I was a cool, dry night - 75m at 3.885 was awesome - I was running ~175w of carrier output and worked
WA1HLR in Maine
W4BVT in Virginia
KX5JT in South Louisiana
K4KYV in Woodlawn, TX,  with compliments on the mobile signal, from all.
Don said he'd been listening to us for a while before broke in because he was working on some project, using both hands, but was listening for an hour or more.  Tim and I are known for making buzzardly transmissions ;-)

~shrug~ 
Some days you're the bug...
Somedays, you're the windshield. 

You give me an interesting idea, though, Carl... 
Do you (or anyone reading) have a source for air-dux type coil-support rods?  I think I'm gonna make my own, out of 10ga wire, space it at 6 t.p.i, make it 10" long and 6" in diameter.

Hmmm.. I think I found what I'm looking for...
#6160 COIL

The #6160 coil is 6 inches in diameter and is wound with 12 Ga. wire at 6 turns per inch. It is 10 inches long and will give excellent performance on 160 meters.

A 20 inch capacity hat and a whip at least 78 inches long will be required.

 Operation on 75 and 40 meters will be possible but tuning oh the higher bands may be troublesome because of the excessive shorted turns.

Yup - sounds like what I need.  Was gonna go with that, until I looked a bit farther...

LOADING COILS # 6160 Coil (80 - 160) --------- $300.00 (Special Order)
# 6160 Coil (80 - 160) --------- $300.00 (Special Order)
http://www.maintradingcompany.com/main/page_texas_bugcatcher.html

Wowzers!

Back to winding my own...
anyone have a source for Air-dux style glass support rods?