[amsat-bb] CP antenna build: unexpected discovery

[Norm n3ykf]

Hi all!

Built a 2x10 CP UHF antenna. Started with an Arrow 437X14. Two 7
element antennas on the same boom.

Added three sets of elements. Have been using this as a linear antenna
in my satellite rig. It's been performing reliably for three years,
including all DX trips

This is one of those projects that took a lot of learning, mostly how
to use the analyzer and become good at SMA connectors.

Pic of the antenna here:

https://www.flickr.com/photos/n3ykf/44365875084/in/dateposted/

The next three photos are of the scans made at the end of the project,
verifying CP, +/- 90 degrees. Note that the offset from the adapters
has to be figured in. 18.3 degrees.

Using three 9V rechargables in series to make the +V to drive the
relays. RG-142b/u and SMA male connectors both from ebay.

Got out to play with it a few days ago. The CP rig doesn't appear to
add much to the received signal where there is no obstruction. It does
make a noticeable difference toward the horizon where trees come into
play.

While measuring parts, I found that the little 26VDC SMA relays
measured out NC and NO to 231 and 231.8 deg respectively. The actual
path: 4.5cm. HUH?

Managed to damage one of the relays. Bypassed the center pin crushing
the female contact in the relay. So I took it apart. Nothing inside to
justify an unusual measurement.

Pics here:

https://www.flickr.com/photos/n3ykf/44604433654/in/dateposted/

The SMA jumper that was made using 90's and adapters to connect NC->NC
measured out to 281.3 degrees. Path measurement: 9.5cm. Another
surprise.

Doing the math, the relays appear to have a velocity factor of .1(back
of the envelope math). Is this for real? A surprise considering that
I've never seen anything with that low of a parameter.

Catch you on the birds

Norm n3ykf