Protect your whip!

[mrwalsh85]

Hey guys, I've been working on a new av bay for my Dynacom Anaconda, and needed to protect my antenna for my TeleMetrum.

Initially, I was going to drill a hole, that was a snug fit for the as-supplied antenna with the TeleMetrum, and have the remainder exposed in the recovery bay.

After monkeying around with the av bay for a bit, I realized that there is a very real risk of damaging the antenna.

I recalled that @Danno had experimented with 3D printed sleeves for his antennas, and I recall that they didn't survive (at the time).

I finally got to the hobby shop today and picked up some r/c antenna sleeves and took them to my shop promptly to see how they fit.

Good news, even if your antenna is not the straightest - it will still slide in with some resistance - but if they are straight, they will slide right in.

Now, I wasn't sure how to secure the antenna sleeve in the bulkhead.... At $1 per sleeve, I wasn't afraid to experiment.



I thought to myself - what if I run a countersink in reverse to flare out the sleeve? Went out to my machine shop and grabbed a countersink, chucked it up in the ol' Dewalt and spun it up in reverse.



Good news - it did exactly what I wanted! Next - I had to open up the hole that I had already drilled for my antenna - turns out the sleeve is 0.123" - perfect for a 1/8" drill bit. Grabbed one of those and went to town.



Assembled everything - and it looks great! I will probably grab a scrap piece of G10 and drill a 1/8" hole and see how well these sleeves accept CA. If they do, great! If not, maybe a strategically placed ziptie against the outside of the bulkhead, preventing any movement of the sleeve.



Now I will say I haven't tried this in flight, but I'm looking forward to it, I think it will hold up decent. And for the cost, I can afford to swap out the sleeve, if needed.

Just thought others might be interested in this.

 

[Buckeye]

What is the risk to the antenna? Getting tangled in recovery gear or burning from the ejection charge?

That's a pretty long antenna on the Telemetrum.

 

[cwbullet]

What is the risk to the antenna? Getting tangled in recovery gear or burning from the ejection charge?

That's a pretty long antenna on the Telemetrum.

I would say that is a pretty good list of the risks.

 

[cerving]

Yup, the R/C guys have been using those plastic tubes like forever... they work great. Try using hot melt glue instead of epoxy, the epoxy isn't going to take to those polyethylene tubes very well. The 70 cm Telemetrum has a longer antenna than a 900 MHz unit because of the wavelength... it's about 170 mm long vs about 80 mm long for a 900 MHz transmitter.

 

[Tobor]

I think a better alternative would be to have the TeleMetrum's antenna pointing in the other direction. I did this with my 6" Stinger.

 

[mrwalsh85]

Yup, the R/C guys have been using those plastic tubes like forever... they work great. Try using hot melt glue instead of epoxy, the epoxy isn't going to take to those polyethylene tubes very well. The 70 cm Telemetrum has a longer antenna than a 900 MHz unit because of the wavelength... it's about 170 mm long vs about 80 mm long for a 900 MHz transmitter.

Thanks for the insight! My thinking is that even if this doesnt stay put, at least it'll protect the antenna long enough for me to find my rocket.

I'm looking forward to trying this. If it works well, I'll likely adopt it to the rest of my rockets using the TeleMetrum. The original setup I had had a hole that was seemingly a light friction fit for the insulation on the antenna, I was worried about the sharp corner at the bulkhead shearing the wire (yes, I could countersink it, but I think the concern remains). Additionally, I have a better chance of keeping the antenna straight - though probably not a problem for the altitude this rocket will fly to (~15k, 20k max) - but if it works, I will have more confidence going highter with a straight(er) antenna.

Just thought I'd share the tip for anyone interested, is all.