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I will be on Mt Greylock in Western Mass this weekend for the September VHF/UHF contest. The W2SZ group operates 50, 144, 222, 432, 903, 1296, 2304, 3456, 5.6 GHz, 10 GHz, and 24 GHz.
Visitors, guest operators, and/or grunt labor welcome and appreciated.
Setup Thursday, Friday Saturday, Operate Sat and Sun, take down Monday
jeff, wa1hco
I don’t know how to answer the question about modifying the center pin. But, I can comment on grounding and protection strategy.
The J-Pole antenna has the center conductor connected to the ground through a quarter wave shorted stub. At the frequencies of lightning and static discharge (KHz and low MHz), the J-Pole shorts the coax center to shield. There is little benefit for a coaxial surge protector type device.
The risk to a radio is from the lightning surge current on the _outside_ of the coax conducting _through_ the radio and power supply to the power line or computer equipment connected to the radio.
Most of the protection from a coax surge protector comes from grounding the device near the station ground, assuming the radios and other equipment are also grounded.
The best approach is to surge protect the power lines and connect the green wire ground to the coax shield so the current has a better path _around_ the radio rather than through it.
My cheap low power solution is to get a surge protected power strip with two F connectors. Then loop the coax from the radio to power strip then to antenna. I have used this successfully at 100W on HF and at 50W on VHF. Also plug any computer or audio equipment into the same outlet strip.
Yes there is a mismatch between the 50 Ohm radio and the 75 Ohm F connections, but the length of the 75 ohm portion is short compared to 2 meters so adds little SWR to the system.
Also, internet connections are a big risk because they connect to long external wires. I use WiFi or Ethernet over fiber to isolate the shack computers from the wired internet.
jeff, wa1hco
The idea behind looking at elevation plots is to figure out if there is significant energy directed low for DX or high for local communication. The higher the dipole, the lower the first lobe. Also, a high antenna is typically able to look over nearby obstructions. Some people place two or more antenna spaced vertically and switch them with an upper/lower/both switch. This has the effect of moving the peaks and nulls around and upper or lower can work better depending on propagation.
Some sort of elevation pattern effect occurs with any terrain slope around the antenna, but the peaks move around for each installation…hard to predict.
Another way to think of it…the ground is a mirror and a mirror image virtual antenna acts to beamform the signals. An incoming ray is received by both real and virtual antenna and the signals are summed. This is the same as the real antenna receives both the direct path and the reflected path from the ground.
On average, antenna works better at higher elevations. You don’t really perceive he nulls when operating, it just seems hard to work some stations. But the next day, the ionosphere is at a different height, the bounces change and the the null moves to make a different location harder to work.
I tried N1MM+ on Ubuntu with virt-manager (open source alternative to Virtualbox) and Windows 10 guest. It appeared to work better than the last time (3 years ago). It connected to the IC-7300 via serial USB.
I’m not an expert at N1MM+ setup and didn’t try it extensively, but it did work without any glitches…so far.
This was my first try at virt-manager instead of Virtualbox. I like it. The vm uses the same virtual disk image as Virtual box, so no need to reinstall. I did install Ubuntu as a guest using the .iso file and it went fine.
N1MM is able to launch and interface with WSJTX, but I could not get that to work correctly.
jeff, wa1hco
N1MM does not run in Wine and the authors said they could not support Linux because their audience didn’t want it and they are busy. I got it running under wine but something about the event loop running in the background caused persistent screen flicker and poor response to key strokes and mouse input. That was 3 years ago or so. It’s also when a friend introduced me to the lead for N1MM and we talked at Boxborough about lack of support for Linux.
For my needs, Gridtracker, WSJTX, PSKReporter all work fine under Linux.
CQRLog appears to be popular, but uses some database stuff that exceeds my attention span to setup. But I’m running a bleeding edge Ubuntu that may not be supported well.
Sometimes I spin up a Windows VM under Virtualbox, but ham apps tend to stress certain realtime or I/O features that give me problems.
So, my WSJT stuff is fine, but I can’t log SSB or CW contacts, at the moment.
jeff, wa1hco
I bought my first house in North Attleboro, MA…on low ground.
I took my IC-211 up to the second floor unfinished bedroom and set it on the floor the connected a quickly made dipole and set it on the floor next to the radio. I sat down on the floor as well.
Some tuning around on 2M SSB showed some activity…which is unusual. I heard a station with a Southern accent and tail ended their QSO, the 4 came back to me and I worked North Carolina on 2M SSB with 10W. Really good tropospheric ducting that day.
jeff, wa1hco
A followup about the settings for pskreporter.
On all bands, show signals, sent/rcvd by, grid sq, fn42 using FT8, over the last 15 min
Bold text means value in a selection or text box.
The receiver pulling 0.17 A may be ok. The 0.5 A specification is probably a maximum with audio unsquelched and volume turned up. Mobile rigs have a lot of power for the speaker to overcome road noise.
“12V” on a lead acid battery is about 13.6V with no load/no charge and rises to about 14.4V under charge, but varies with temperature. What does the voltage do when transmitting? If it drops, then look for a bad connection?
Another thing to look for, do the panel lights on the radio dim when transmitting? (they should not)
jeff, wa1hco