Author: John Kaufmann via Topband <topband@contesting.com>
Date: Tue, 23 Feb 2021 13:25:53 -0500
Some of you may have seen the article by WD8DSB in the latest issue of QST. I believe WD8DSB is on this reflector. His article describes a mini-flag antenna that can be used for direction-finding. Th
Author: Steve Lawrence via Topband <topband@contesting.com>
Date: Tue, 23 Feb 2021 10:59:04 -0800
Yes very nice article and design by Don. Flags/loops do not exhibit gain but rather directivity. The larger the loop the greater the capture area and the less of a need for a preamp. I routinely use
For finding 160 meter noise sources, I use a C-Crane or Sangean pocket AM band radio tuned to 1710 kHz. It also has a very sharp null due to the ferrite loop stick antenna built in. The QST antenna d
HI Steve, Thanks for the nice implementation comment. The portable flag front to back ratio is highly related to the elevation angle and frequency of operation (just like any terminated loop), and th
Author: John Kaufmann via Topband <topband@contesting.com>
Date: Tue, 23 Feb 2021 18:37:03 -0500
As a follow-up to my original post, here are a few additional comments. Don, you mention that you designed the mini-flag for a deep null off the back at low elevation angles, which is entirely unders
The smaller the flag the lower its gain and its signal output. The limit of usefulness is reached when a weak signal is below the thermal (Johnson) noise of the system (~ loading resistor). Below thi
Don. . .thank you for the very nice loop article in QST. And, thank you for your generosity of not taking compensation to help make it affordable. The loop antenna would be a very useful tool to h
Hi George, Thanks for mentioning that antenna system thermal noise eventually establishes the limiting factor where additional preamp gain will not provide any additional improvement in performance.
Hi Dave, How about an SDR (e.g. RSP1A, Funcube dongle or even RTL dongle) and a small laptop or tablet? That way youd get spectrum and waterfall as well as audio. And you can record everything for a
Bi-directional loops lose their directivity for the most part, when being applied to skywave signals. Is this mini-flag still unidirectional on skywave? I would think not, but must ask. 73 Rob K5UJ _
Hi Rob, Front to back ratio all depends on the arrival angle of the signal, and the portable flag directional properties are just like full size flag directional properties assuming you select the ap
Don, I put that note out because friends were asking if with a "ultra-low-noise" pre-amp they could use it for DX. Unfortunately, that's not the case. (I have tried.) Of course, that does not diminis
something portable to home in on it. Do you or anyone here any suggestions for a reasonably good portable receiver with an external antenna jack (might be hard to find?) that will cover the 160m ba
Don's directional loop should significantly reduce my tracking time for most common switching noise in the neighboring area. I currently use a National RF loop + preamp with an SDR-IQ receiver strapp
On 2/24/2021 6:32 AM, GEORGE WALLNER wrote: Don, I put that note out because friends were asking if with a "ultra-low-noise" pre-amp they could use it for DX. Unfortunately, that's not the case. (I h
Hi George and gang, I really appreciate you as well as Steve WB6RSE making sure folks understand there are performance limitations when using very small antennas such as my portable flag as a dedicat
Hi Dave, I hate to recommend anything and others have given you some good recommendations, nevertheless I will make a few comments. My workhorse radio for direction finding is the good old Realistic
Hi Rich " The problem here is that any loop antenna inherently has a noise temperature of 300K, because it is lossy, and because it "sees" the earth" Would you elaborate on that? Small loop 1/10 of w
Hi John, You started this mess (or maybe I did), and finally here is my response to a few of the questions you had and thanks so much for waiting in line for my response. 1) As I have mentioned in a
I have read some negative info on the Malahit (the EBAY clones especially, the Russian originals seem better) but it might be OK for RFI investigations. N9EWO Review : Russian Malachite / Malahit DSP