Don't have any updates to add. Still waiting on the band pass filter from china. I also ordered more UHF ferrite snap-on's.
RF efficiency has dropped slightly from ~95% to ~92%. This got me curious so I hooked up my RTL dongle and took a look around. I did not check the frequency when I installed this but it is currently transmitting on 433.765MHz. I don't know if it drifted down but I am hearing something else on the same frequency so I'll keep watching it to see how far it drifts. And it seems that despite me living in a semi-rural area on the edge of town there are still quite a few 433.92MHz devices around.
I played around with EZNEC a little today and modeled a vertical dipole using 24ga solid copper wire with insulation on, just messing around, simulating some Cat3 telephone wire I have. In case anyone is curious the impedance and reactance doesn't change much between 433.92 and 433.765 and if you were to measure the SWR you likely wouldn't be able to tell a difference.
Elevation plot of the vertical dipole 4ft above average ground (about the height of my enclosure). No sense in posting an azimuth plot since it will be a featureless circle.
![[Image: NIleQvN.jpg]](http://i.imgur.com/NIleQvN.jpg)
For those curious about the specifics of the model, I measured the 24ga solid wire at .5mm in diameter and the insulation was .25mm thick. Using that and HD polyethylene as the dielectric (Diel C of 2.3) I got resonance with 155.5mm for each leg of the dipole at 433.92MHz. The resonant length will obviously vary with insulation thickness and type and conductor thickness.
Before I forget again. Here's what I did with the ferrite snap-ons.
![[Image: EuCCPuZ.jpg]](http://i.imgur.com/EuCCPuZ.jpg)
And for what it's worth, it appears the rubber ducky has a small length of coax going up inside of it. That means the antenna does not begin at the connector and that adding anything at the connector would not be at the feed point of the antenna. It would amount to connecting something to the shield of the coax in the middle of the coax, and who knows what effect, if any, that would have. I did order some chassis mount connectors from ebay and when I have time I'll build a little ground plane antenna just to mess around a little.
RF efficiency has dropped slightly from ~95% to ~92%. This got me curious so I hooked up my RTL dongle and took a look around. I did not check the frequency when I installed this but it is currently transmitting on 433.765MHz. I don't know if it drifted down but I am hearing something else on the same frequency so I'll keep watching it to see how far it drifts. And it seems that despite me living in a semi-rural area on the edge of town there are still quite a few 433.92MHz devices around.
I played around with EZNEC a little today and modeled a vertical dipole using 24ga solid copper wire with insulation on, just messing around, simulating some Cat3 telephone wire I have. In case anyone is curious the impedance and reactance doesn't change much between 433.92 and 433.765 and if you were to measure the SWR you likely wouldn't be able to tell a difference.
Elevation plot of the vertical dipole 4ft above average ground (about the height of my enclosure). No sense in posting an azimuth plot since it will be a featureless circle.
For those curious about the specifics of the model, I measured the 24ga solid wire at .5mm in diameter and the insulation was .25mm thick. Using that and HD polyethylene as the dielectric (Diel C of 2.3) I got resonance with 155.5mm for each leg of the dipole at 433.92MHz. The resonant length will obviously vary with insulation thickness and type and conductor thickness.
Before I forget again. Here's what I did with the ferrite snap-ons.
And for what it's worth, it appears the rubber ducky has a small length of coax going up inside of it. That means the antenna does not begin at the connector and that adding anything at the connector would not be at the feed point of the antenna. It would amount to connecting something to the shield of the coax in the middle of the coax, and who knows what effect, if any, that would have. I did order some chassis mount connectors from ebay and when I have time I'll build a little ground plane antenna just to mess around a little.