ARRL

KE4NHW

Joined: Sat, Mar 17th 2012, 23:02 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
RFI 20M PSK31 Frequency Feb 8th, 15:01 2 149 on 8/2/15
Schematic for auto-switching LC Network Tuner May 4th 2012, 13:25 1 1,208 on 4/5/12

Latest Posts

Topic Author Posted On
RFI 20M PSK31 Frequency KE4NHW on 8/2/15
I forgot to mention that the interference is very specific to that frequency: moving off frequency even the requisite 3kHz totally eliminates the pattern. Hopefully someone can solve this mystery and determine if there is a solution that the IARU or the FCC could pursue.
RFI 20M PSK31 Frequency KE4NHW on 8/2/15
For about the last month or two I have noticed a strange interference pattern on 14.070 MHz. The interference pattern can be most clearly seen in the waterfall at about 1800Hz to 2050Hz. These lines are evenly spaced at nearly 50Hz separation. Also, when I do not have a strong PSK31 signal coming in these lines appear across the entire 3kHz of the frequency, again spaced at 50Hz intervals. I have tested and determined these are not computer artifact. The strongest of these occurs at 1931Hz, and could easily be confused with a carrier if it were alone. I have asked several times on the frequency, and individuals at very different geographical areas are also seeing the same interference pattern. Some areas confirming are Canada, California, and Europe.

I have run very thorough tests on this end and determined the cause of the interference is not here. Moreover the reports from distant locations at times that I am not transmitting confirms something else must be the cause. Has anyone else seen this, and does anyone know what it is? Finally, is someone looking into a solution for this interference or is it unresolvable? For any interested persons I can save and provide screenshots of the noise.

Thank you for your input on this and 73.
Schematic for auto-switching LC Network Tuner KE4NHW on 4/5/12
I am considering a long wire antenna for an apartment installation, but I need the ability to match impedance at the antenna feedpoint, as it will be fed with coaxial cable. The setup would be: TS-430S > AT-250 Tuner > Coax > AutoSwitching Multiband LC Network > LongWire

I want to homebrew this design if possible. The key is to have a MC to count the frequency and select the appropriate LC network for use. The design would be for General Privs, so each LC network should bring the longwire into match for the center of the operating range (separate LC's for CW portions and SSB portions of bands when relevant, so some bands will have 2 or more networks). The goal is to get the match as close as possible at the feed point and let the AT-250 do the rest. I want the majority of the matching to occur at the antenna to maximize power transfer to the wire.

The device should be fully automatic and require little to no interaction, and will be built in a weatherproof housing and sealed. Preferred that it is DC powered. Does anyone know of a schematic of such a device, one that is capable of being a homebrew? Please let me know.

Back to Top