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W1VT

Joined: Sat, Apr 4th 1998, 00:00 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Antenna analyzer vs feedline type Sep 21st 2012, 14:37 1 1,561 on 21/9/12
USB to Serial Port problems--Prolific Drivers Aug 3rd 2012, 18:27 1 1,804 on 3/8/12
Italian Phishing emails! Dec 13th 2011, 14:20 1 1,473 on 13/12/11
John K0GMO needs help designing SS Amp Nov 17th 2011, 15:53 1 1,363 on 17/11/11
1 Farad Capacitor to Eliminate Headlight Flicker? Oct 19th 2011, 13:14 4 2,354 on 9/11/11
History of Relay Rack Dimensions? Oct 17th 2011, 12:58 2 1,591 on 25/10/11
Miswired Selsyn Oct 13th 2011, 17:51 1 1,417 on 13/10/11
Stealth Antenna wire Sep 12th 2011, 12:51 2 2,033 on 13/9/11
Designing a ham bench Aug 29th 2011, 12:38 2 2,208 on 29/8/11
Can't find recent Hint and Kink Aug 26th 2011, 13:01 1 2,043 on 26/8/11

Latest Posts

Topic Author Posted On
J-Pole Ladder Line Questions banfred 13 hours, 48 minutes ago
You sometimes get Sporadic E skip propagation on 52MHz, which converts the linear polarization into elliptical polarization, which would be compatible with a horizontally polarized J Pole.

http://en.wikipedia.org/wiki/Sporadic_E_propagation

http://forums.radioreference.com/amateur-radio-general-discussion/268257-lets-talk-about-6m-fm.html
discussion of 6M activity

Zack Lau W1VT
ARRL Senior Lab Engineer



J-Pole Ladder Line Questions banfred 17 hours, 4 minutes ago
2M FM is almost entirely vertically polarized--the most common exception are satellite transmissions. Mounting it horizontally would result in cross polarization to normal 2M FM transmissions, resulting in a large loss in signal. You are also likely to see a detuning effect from mounting it close to building materials. The antenna tuner isn't likely to help--tuners are much harder to build at VHF as compared with HF, so they aren't as common. Also, the higher line losses at VHF make them much less effective than at HF.

Zack Lau W1VT
ARRL Senior Lab Engineer
KX3 on PSK31 using Signalink & Digipan KZ6B 1 day, 13 hours ago
Quote by KC1YC
Hello KC1YC here,

I am new to PSK31. Have an FT-817ND set on full Power. SWR fine into AlexLoop (indoors). Transmits fine with Mike and ssb. SignaLink between rig and computer. Receives fine, On transmit, rig is triggered (transmit led comes on) but power is nil on external meter (normal indication when using Mic).


That indicates that you don't have audio on the headphone or speaker output making its way to the radio. You might try listening for it--disconnect your rig temporarily and use a computer speaker or headphones to hear it. A computer typically has more than one volume control window--you may need to hunt around to find the right window.

Once you get that sorted out, the next step is making sure you have the proper connection from the computer headphone output to the mic input of the rig.

Zack Lau
ARRL Senior Lab Engineer
Return Loss Bridges WB5EMX 3 days, 20 hours ago
The return loss bridge can be used to characterize the impedance transformation of a balun--how much it increases the SWR of the system. In practice, this isn't as important as the loss of the balun, as most hams have a tuner to compensate for a mismatch created by the balun.

http://www.w8ji.com/balun_test.htm
http://karinya.net/g3txq/chokes/
Typically you want something that will accurately measure high impedances to characterize the choking impedance of a balun.

How to Evaluate Your Antenna Tuner - Part 1
QST April 1995, pp. 30-34
With some simple low-power measurements you can learn a lot about your antenna tuner. There may be some real surprises.
How to Evaluate Your Antenna Tuner - Part 2
QST May 1995, pp. 33-37
AI1H shows data taken using a low-power SWR tester and his simple load boxes to evaluate several antenna tuners.
These two QST articles show a clever way to determine tuner loss.

You can certainly use a signal source, detector, and a return loss bridge to characterize an antenna, but most hams find it more useful to use an antenna analyzer, which is a portable box that combines all these functions--the newer ones will even plot out the results on a graph--great for people who need a picture.

When making SWR measurements it is important to filter out harmonics--either at the detector or signal generator. You won't get accurate measurements with a square wave and a diode detector!

Zack Lau W1VT


Heathkit HW-101 and SB-620 KC1DAK 6 days, 16 hours ago

Here is a very informative article on modifying the SB-620 for a 3395kHz IF, if that SB-620 is set up for something else.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCYQFjAB&url=http%3A%2F%2Fwww.tronola.com%2FConverting_the_Heathkit_SB-620_for_3395kHz_IF_Receivers.pdf&ei=rsPsVOLVGfiOsQSar4CwAw&usg=AFQjCNEFlmeXjlHBGVlp0fyh96ts0if2Tw&sig2=G0OwN7HV-c5UNLuRfyxuZg&bvm=bv.86475890,d.cWc&cad=rja


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