Topband: Early Pioneers
My Dad, 2NJ, is in the 1916 book - which I have a prized copy of. If anyone has books or supplements earlier - I'm collecting 73, Hal N4GG (Harold Kennedy Jr., Harold Kennedy Sr. was 2NJ) ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Homebrew Hairpin
I have matched quite a few Tee top verticals - and do it as follows... Put an antenna analyzer at the feedpoint and measure what you have at the QRG you want - probably 1.830? Put the numbers into the TLW program and let it design an L network for you. Wind the L and use transmit quality surplus caps for the C. I can supply a coil winding Excel spreadsheet off the list to help get the coil wound. For coil forms, in the US, Target stores sell drinking cups that are about 3 in diameter and are made of polycarbonate, which is an excellent choice for an HF coilform. They are about $1. Buy one the color you like, cut the bottom off and wind the coil on that. Not much to it - always seems to work the first try. The only occasional issue is a strong BCB station may confuse the antenna analyzer. 73, Hal N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Chokes, et. al.
Common mode chokes DO NOT belong between boxes on your desk. As Tom and others have said. The objective is to get them all at the same RF potential, not isolate them from one another so they can seek their own independent RF potential. 73 Hal N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: UFOs
Has anyone ever seen or can point us to a decent treatise on identifying UFOs? That would be: Unidentified Ferrite Objects. Yes, I can throw a few turns on a UFO and sweep it and zero in on the material, maybe make an educated guess at that point as to the manufacturer, check his data sheets for a match and data sheet (unless its Laird) and to be honest, as skilled and test equipment-rich as I am in this area I would not feel comfortable having gone through that rather laborious process that I really knew what I had. There must be a google of UFOs for sale at hamfests and surplus houses - never getting bought or used since we can't ID them. Anybody want to design up a UFO tester? Hal N4GG Happy 4th ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: THeory
A common quip running around the system engineering department I ran for years: Sure it works in practice...but what about in theory? Happy Thanksgiving everyone... N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: RFI
I have had two instances over the past few years of similar noise Mike. Both cases turned out to be small switching power supplies...one for a Dell laptop, the other for an LCD monitor. Both supplies were very quiet under normal circumstances, but were laying on the floor along with lots of coax including the feedlines for the low-noise receiving antennas. When my feet would move things around under the op table, sometimes one of those two supplies would wind up on top of or next to a low-level coax. The coupling was magnetic, not RF. Switching power supplies radiate a magnetic field and coax is not shielded cable WRT to a magnetic field. A magnetic field will produce unequal current in the shield and center-conductor of coax. Moving the little switchers off the floor solved the problem. SteppIRs and other new gear often come with their own switching power supplies. The 33 V StepIR supply is A LOT noisier than the standard 24V one BTW. 73 Hal N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
