On 3/20/2011 3:09 PM, JIMMIE wrote:
On Mar 19, 5:59 pm, wrote:
On 19 mar, 22:25, wrote:

I was palnning on building a 2M Yagi this weekend and was wondering if
my available bill of materials would have a significant effect on
normal design parameters. The plan is to use 3/4 inch EMT conduit for
the boom and 3/8 inch all-thread for the elements. My concern was that
the threads could change the design frequency.

JImmie

Hello Jimmie,

I think it will be OK, but if you want to be 100% sure, make a dipole
of same thickness tubing and one from the threaded material of choice.
If results are same, you can use it without dimension scaling. Are
you using galvanized or alu material?

If required, apply some corrosion protection.

With kind regards,

Wim
PA3DJSwww.tetech.nl
.

Galvanized, The pupose was to demostrate that materials can often be
adlib and still have a useable antenna. Maybe this one will not last
30 years before it corrodes away but probably 5 or 6. Also I want to
demonstrate the value of using a jig when building many antennas all
made the same. I have tried the test you mention on 10 meters before
replacing a vertical mounted on my truck. Changing materials didn't
seem to make much difference. WIll try the same for 2M but I dont
have an SWR meter for 2M at this time.. Was hopng someone in the group
might think this interesing enough to try.


Jimmie

I made a j-pole from galvanized steel. It worked beautifully. When I
replaced it with a commercial antenna I notice very little change in
performance and signal strength. I had hoped my kluge was deficient in
performance compared to the commercial antenna. Didn't seem so. My QTH
was way out in the country side about 20 miles from the nearest repeater.

Just a story for you, no hard data. Sorry.

John