(Now a bi-weekly program)
October 16, 2012
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Homebrewing
VHF/UHF Antennas
Overview
In this episode we discuss and illustrate examples
of getting on the air with 6m, 2m and 70cm (440 MHz). Most of us know the
"mechanics" of HF operation, but VHF and UHF throw some interesting curves at us
as far as propagation, feedlines and losses, antenna polarization, power levels,
terrestrial impediments, and more. Everything from HTs to mobile rigs, to base
stations. And every kind of operation: FM repeaters; point-to-point using FM,
SSB and CW; weak signal propagation; satellites; EME and more.
73, George N2APB & Joe N2CX
Audio Recording
... (Listen
to the MP3 podcast)
Discussion
Notes:
<20:32:00> "Joe N2CX": Marc Franco's MP3 interviews
are not on the whiteboard.
<20:46:34> "Alan W2AEW": I have a picture on mine
<20:46:46> "George - N2APB": Me too!
<20:55:54> "Ray K2ULR": PL is also called CTCSS Continuous Tone coded squelch
system
<20:56:10> "John ZL1AZS": To add your pic to the right-hand panel (with your
name selected in the left panel) right-click your name and go to Select Avatar,
choose a pic from your local hard drive and Voila!
<20:56:56> "Ken - VA3KMD": Joe; what's the upper frequency limit of the N2CX
choke balun kit?
<20:57:41> "Joe N2CX": I've charazcterized it up to 6 meters. A different
ferrite core would make it usable up on higher frequencies.
<20:58:02> "Joe N2CX": John, thanks for the phot ino!
<20:58:47> "Ken - VA3KMD": Thanks Joe
<21:00:02> "Joe N2CX": Alan you need to escape from that Tektronix prison!
<21:00:56> "Alan W2AEW": sometimes I reeeeallly get into my work!
<21:01:21> "Terry WB4JFI": I belive microwave ovens are around 2455MHz, and can
have high-power maggies.
<21:01:58> "Joe N2CX": Hmmm is that pix what you call a green screen?
<21:02:31> "Alan W2AEW": uWave ovens are indeed in the 2.40 to 2.50GHz frequency
range - the same as the 2.4GHz ISM band used for WLAN, Bluetooth, etc.
<21:03:38> "Terry WB4JFI": microwvae ovens operate (hopefully) at the resonant
freq of water molecules
<21:15:49> "Ken - VA3KMD": The Arrow Antenna 2m/70cm Jpole @ $40 works well for
me.
<21:18:36> "Terry WB4JFI": Skip Teller has had several good articles in QST
about homebrewing 2M and 440 antennas of various types. Low cost, fairly easily
found parts, and most are collapsable & easily transportable.
<21:20:08> "Clint ka7oei": A bad antenna outside fed with mediocre coax will
almost always beat a decent antenna indoors... (building materials impose 10-20
dB loss - far more than a likely coax run!)
<21:21:08> "Frank N3PUU": but dont be afraid to run whatever you can.. my most
memorable contact was NJ to vancouver island on 6 meters using a 6 meter dipole
in my attic!
<21:21:22> "Clint ka7oei": RG-6
<21:22:08> "Alan W2AEW": my pic is taken by convertng NTSC video from my camera
to X, Y and Z drive signals for my scope, and thus displaying composite video on
the scope. Then, I took a picture of that
<21:22:17> "Clint ka7oei": oops RG6 TV coax works surprisingly well - the
impedance mismatch isn't really that big of a deal when it comes down to it: Tha
adapters will probably cost more than the coax run
<21:25:41> "George - N2APB": Great point Clint. Often the TV coax can be found
locally.
<21:25:45> "Clint ka7oei": oops RG6 TV coax works surprisingly well - the
impedance mismatch isn't really that big of a deal when it comes down to it: Tha
adapters will probably cost more than the coax run
<21:26:20> "Clint ka7oei": (Sorry - i was typing and forgot to mute the mic -
and spacebar toggles the mic...)
<21:26:23> "Paul PA1TAS": Great show thou and was late in but great as always
thank you very much from Holland
<21:26:48> "Frank N3PUU": Thanks guys, great job! See you on saturday.
SESSION NOTES
....
Higher the
better!
Mostly line
of sight communications
- Why are repeaters usually located on hilltops?
Radio Mobile web site (Line of Site/Nape of the Earth VHF propagation):
http://www.cplus.org/rmw/english1.html
30 MHz path between N2CX ("map pin 1" in Brooklawn, NJ) and
N2APB ("map pin 2" in Forest Hill, MD)
30 MHz propagation probabilities from QTH of N2CX, based on terrain and
elevation
146 MHz propagation probabilities from QTH of N2CX, based on terrain and
elevation
Marc
N2UO
