Ed et al, My apologies for the incomplete email. In my attempt to keep my response brief, I was perhaps brutally brief.
In my efforts to understand and control the contributing factors of site correlation, I had sent my antennas to Liberty Labs. I spoke with their President, Mr. Mike Howard about my needs. Mike was very helpful in explaining the evolution of bicon antennas and pointed out the differences that I should expect. In fact, he was right on the money. The "older" model that I have is an EMCO 3104C. This model is calibrated with an orientation marker as the balun is apparently not balanced as well as later designs. According to Mike, EMCO also sells models that are matched and have stubs to control the effects of self-resonance at a particular frequency. Mike had informed me that the EMCO 3110 was a "newer" model that had overcome some of the old problems of balance. This appears to be the case as it was our 2 year old 3110 that exhibited the <1 dB variation with polarity and geometry, v and h, 3 and 10 meters. The 3104C was at our company long before I came aboard. I should have had it checked for proper operation prior to calibration as one respondent had suggested he does as a matter of routine. The performance of my 3104 may be due to design limitations or due to previous use of an unknown nature. That's my next step. My thanks to the many people who have made this discussion a lively, informative dialogue. Regards, Don Umbdenstock Sensormatic ---------- From: [email protected] To: UMBDENSTOCK, DON Cc: 'EMC-PSTC Discussion Group' Subject: Re: Antenna Calibration/Site Attenuation List-Post: [email protected] Date: Tuesday, August 26, 1997 12:32PM --- On Tue, 26 Aug 1997 08:12:00 -0400 "UMBDENSTOCK, DON" <[email protected]> wrote: > > Great dialog, just the path that I was hoping would develop. > > One thing I have learned since the question was first asked, all > biconical antennas are not made equal. The original antenna calibrated > at an outside test organization, exhibited a 5 dB difference between the > vertical and horizontal polarizations at 3 meters in the frequency range > of 30 - 50 MHz. > > Another antenna subsequently calibrated at the same organization had > less than 1 dB difference between v and h, 1m and 10 m. This outcome > was more in line with the expected outcome of the calibration per C63.5 > which stated "minor variations with polarizations and geometries" where > geometries is understood to mean test distances. > > Don Umbdenstock > Sensormatic ---------------End of Original Message----------------- Don: Not meaning to single you out, but your post tweaked a concern of mine. Are we all operating in a sense of fear in this forum? Do we really have to obfuscate the facts by referring to an "original antenna" and "another antenna"? Or am I the only one who would like to know exactly which antenna and test lab that you're talking about? Ed -------------------------- Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: [email protected] Date: 08/26/97 Time: 08:32:35 --------------------------
