On 8/13/2025 9:37 AM, Steve Jones wrote: Brian, How about one vertical antenna on one RX and one horizontal antenna on a 2nd RX, with the two signals combined in diversity mode? My K3 can do that. 73
". . . the overwhelming issue for many of us is local noise." Jim, have you tried low horizontal antennas? Even though their response to low-angle signals is inferior to that of verticals, they might
I borrowed a coil from QCoil Inductors to measure with my HP 4342A Q meter. This coil did not have the black, UV-resistant dielectric spreaders of production coils, but it was otherwise the same. Her
"I would guess that the measurement uncertainty (and modeling uncertainty) is sufficiently large that the modeled and measured are the same." Jim, inductance critically depends on coil diameter. But
After further reflection, I think CMRR is a misleading term for what I'm calculating. CMRR is better understood as the ratio of desired power radiated by the antenna to undesired power radiated by th
"3. A common mode choke, like any other inductor, isn't going to have much effect at a current minimum, so placing common mode chokes at current maximum(s) along the coax seems like it would be good
One would need at least a dozen clamp on cores to achieve a significant (> 1K) choking impedance. Thanks for looking up the data, Joe. I have an old K6NA bead choke somewhere in the garage. As I rec
If you had enough extra feedline at the spot you wanted to install a secondary choke, a simple solution for a single band might be a coiled-coax choke. These air-core chokes act as a trap with very h
Here's another offbeat idea. If you have an effective grounding point nearby, you may be able to shunt unwanted residual shield current to ground. The coax need not be severed. However, I would not t
"A coil of coax is NOT an effective choke at HF." Jim, take a look at the reference I provided for a coiled-coax choke I made for the FM broadcast band. It measured 63k ohms at resonance. The impedan
"Again, please study the link I posted." Jim, I didn't see anything in there that addressed a resonant coiled-coax choke. There was something about a "solenoid balun" that provides inductance, but th
"Why sever the connector? If we are talking about RG-213 size coax, that is .405 inches in diameter." Sever the coax. I assumed the desired spot was far from the shack and it would be too much troubl
"But, I wonder, how important is it to have a choke at every current node?" I don't think anyone is proposing that. What I would do is put a choke at the feedpoint. Only if I still had CM problems wo
"This one bothers me. Remember that there really is no such thing as ground for RF - that ground rod is strictly for lightning / static currents. Connecting the shield to a grounding point will simpl
"Except that "ground" isn't actually some sort of sink for RF. Imagine a portable battery operated setup with a dipole antenna and nothing about the rig connected to ground. A common mode choke will
"That's a fallacy. It simply isn't." Dave, it would be helpful if you'd supply your reasoning. In many ways I regard ground as just another conductor. However, unlike a wire, it is normally without r
"The earth is not a sump into which hum, buzz, and RFI is poured!" I think what's going on is that "current sink" means different things to different people. I regard ground as an RF current sink, bu
"Earth ground affects transmitted RF because the radiated RF impinges on the earth and is absorbed and reflected, the ratio between the two being affected by the parameters of the earth (conductivity
"If you connect a wire from any point on the dipole to ground, current will flow." That corrects the typo. I wanted to add that one way to visualize things is to employ the image-current model that a