From Lee Barrett
19 April 2025 -- 10am - 6pm MDT - Doolittle Raid commemoration operation
Slides by Dave Harris
Questions: Email me at jushamn@gmail.com. Put CSERG on the subject line.
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Johnny Rauzi send a link to a website that sells filters for broadcast interference and ham band bandpass filters. These are designed for QRP transceivers such as the Xeigu G90.
Click on this link K9DP Shop
A friend Chazz, K7OVG, and I were talking about a problem with his Xeigu G90. I also talked with another ham having similar problem during Winter Field this year. Turns out they both have been experiencing interference when strong out of band signals were present. In my friends case it was nearby AM broadcast stations. In the other case it was another nearby ham operating on a different band. This is most likely caused by overload of the first RF amplifier in the receiver.
My friend was able to solve the problem by using an external tuner between the G90 and the antenna to act as preselector. (I know, two tuner is supposed to be a bad idea, however, desperate times call for desperate measures.) Back in the "good ol' days", it was common practice to use a preselector ahead of a receiver to solve the same problem. These devices were tunable band pass filters. One would set the receiver to the band of interest, and next set the preselector to the same band and peak the desired signals.
Chazz did the following with his G90. Selected the desired band and tuned the external tuner then pressed the tune button on the G90. He was able to stop the interference. He said he was able to transmit through both tuners without incident.
Try using just the external tuner first to see if it solves the problem. If it does the don't use the internal tuner at all.
If you try this with a different transceiver, bypass the internal tuner while you tune the external tuner. Then engage the internal tuner and let it tune. This lets the external tuner match the 50 ohm input to the transmitter. Then the internal tuner sees a 50 ohm input and adjusts to match it. Now both tuner act as bandpass filter, preselector, ahead of the first RF amp.
Another solution is to purchase preselector. Be sure if you do that there are provisions to bypass the preselector while transmitting. I looked online and found several preselector options. Most of the ones I saw were designated for SDR receivers, however, there may be something out there that has built-in transmit bypass capability.
If you try this, please let me know what you experienced. Send an email to k7pdw@arrl.net and put CSERG on the subject line.
The annual Utah VHF Society Swap Meet will be held on Saturday 29 March 2025 at the Western Sports Park (Formerly the Legacy Events Center) 1049 W Clark Ln, Farmington, UT 84025. This is the same location and building that we have used in the past. Parking is available in the main parking lot or at the east side to the building.
The doors open for set up at 0800 and selling begins at 0900. Members get into the event for free, nonmembers pay a $10.00 entry fee. Tables are $7.00. If you bring your own table a space is $5.00. We only have a limited number of chairs so bring one if you choose to. Sellers please come in and pay for your table before you bring your equipment in. We will have refreshments for sale if you desire, Sodas, coffee, hot chocolate, donuts and snacks.JAN 29 - LEE BARRETT Determining The Impedance Of Unknown Coax
FEB 26 - BYRON HELLEWELL Internet Radio Linking Project
MAR 26 - DAVE HARRIS Comparing Antenna Gain Specifications
APR 30 - ART THOMASON DMR
MAY 28 - MICAH REDMOND Ham Radio Modes
JUN, JUL, & AUG - Summer Vacation
SEP 24 - TBD
OCT 29 - TBD
NOV 26 - Thanksgiving Eve, No Meeting
DEC 31 - New Year's Eve, No Meeting
Conductive fabric is available from Amazon. It make an excellent ground plane in place of long copper wires. Several hams in the area have used this with Wolf River Antennas with great result. It's very light weight and flexible. It does tend to get blown about in windy conditions but following are a couple of solutions for that if rocks are not handy to hold it down
Solution 1 - Grommets
I found the cloth is so thin the grommets pulled out. So my XYL sewed in these upholstery reinforcements and I redid the grommets. I use fishing weights on carbineers to hold the cloth on the ground. Very fast setup and flattens out my SWR across the bands with my WRC and 17' whip. de KJ8MRH
Solution 2 - Bias Tape Edging
I had my wife sew bias tape along the edges. She cut the tape several inches longer than the cloth then folded it back and stitched it to form a loop that could be used with stakes.
