3D printer filament for RF Use

[G4APV]

I've just made a "ice cone" helical feed https://www.qrz.com/db/DC8PAT#IceConeFeed for QO100. It works well on transmit and is ok on receive - allowing for the helix partially blocking the LNB. However these are without the cone that goes over the helix. Putting that on reduces the MER of the beacon on QO100 by about 1.5dB so the material I used to print it is clearly lossy. I used Sunlu white PETG and built the cone without infill.

Has anyone built this, or similar, in which case what filament did you use, what losses did you get, and most importantly, is there a better material to use?

Thanks

Bob
G4APV

[radiogareth]

When the cone was first published I did print one in Prusa PLA. However, I have never used it, preferring the POTY. As my dish is mounted upside down it doesn't get much weather on it anyway. Perhaps you could try that? Maybe just shield the lower part of the helix feed. I have used a PETG fizzy water bottle as temporary (well, now 2+ years so perhaps permanent!) shielding for the LNB which is of course now sticking up towards the satellite.
Worth a try if you like experimenting. It significantly reduces the windage too.
Gareth

[G4APV]

Thanks Gareth, I may well end up with a bottle over it all! I would like to get the cone to work if I can, it looks nice ( ) and is robust. I may try clear PETG and see how that goes. However, as you say the POTY is probably better, certainly it seems to be so on receive (9dB vs 10dB MER on the beacon).

Cheers,

Bob

[g4eml]

There is also the lightweight PLA that is used for printing flying model aircraft. When extruded from the nozzle it foams up slightly to give a much less dense material. I have some but haven't yet tested it's RF properties.

Colin G4EML

[g0mjw]

It is not just the loss that matters but also the dielectric constant. You probably need to make this as close to air as possible, which would mean an open structure, i.e. low infill and thin walls plus a low Er material to start with. Don't use Nylon as it may will absorb water and has a Er around 4-5. ABS seems like a good choice but has an Er of 3. PLA Er is around 2, PETG around 2.4.

Mike

[M0DTS]

My attempts building lenses for high frequencies like 134GHz found that ABS was much better than PLA or PETG.
Shame that ABS is so much harder to print big structures in!

Rob