Antennas: (updated Feb 25, 2002)
8 element, 41 foot boom, mounted at 87 feet. 14.0 dBi gain, homebrew design (pictured on homepage) used for F2 & multi-hop Es: 1.75" diameter boom,center section has .125 wall, all others .062 wall..250" dia elements thru the boom insulated, add 8.7% boom diameter to element length for this boom. Tee match, 1.150" spacing, .250" diameter bars, length = 11.5 inches each side, fed with half wave length coaxial cable balun from UT250 with shorted and grounded quarter wave length stubs each side of Tee match. The grounded quarter wavelength stubs did absolutely nothing for suppressing rain static nor summer time "dry air static" common to this area. Will leave them out next time. Driven element dimensions may be too short as I forgot to re-measure it after final adjustments were made....will do that next time down.So far this cycle this antenna has performed extremely well on the F2 and TEP paths. Its clean pattern has paid off on suppressing noise and local QRM while looking for DX.
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8 element feed point construction with half wave coax balun &
quarter wave shorts to ground:
This antenna was the final choice for the all purpose noise cancelling/MUF antenna. It has a super clean pattern yet and enough gain to be useful. Too much gain would make it harder to use in noise cancelling applications. It is designed for many uses: 1) noise souce antenna for the noise cancelling receiver. 2) a 43 to 51 MHz antenna for observing MUF as the band opens up. 3) as a secondary wider beam width six meter antenna. All of the aforementioned points require an antenna design with a good pattern, resonable gain and good impedance.
Compare the gain-bandwidth of this antenna to the rather narrow gain-bandwidth of the 8 element yagi above. Many MUF indicators are between 40 and 50 MHz. Mounting tests will be be performed first to assure there will be adequate isolation between the 8 element yagi and this one. I do not want any deterioration of the 8 element yagi's performance. They will be 3/4 wavelength apart (15 feet). There should be around 20 db isolation between the two antennas (17 db measured...yuk!). I'm still amazed at the computer performance of this antenna considering the bandwidth....
The boom is 9 foot 7 inch, long 1 inch OD 0.065 wall. Elements are .250 inch diameter alu tubing as usual and are thru the boom and insulated. The driven elements are split in the middle and mounted on Delrin blocks. The phasing/matching lines made from UT141 semirigid coax (only outer conductor used). Impedance of the open wire line isn't that critical and can run anywhere from 70 to 100 Ohms without much effect. Add 5.1% of the boom diameter for thru the boom insulated compensation to the element lengths for this boom. Results of testing will be posted when I get them. Antenna seems to perform as expected. Better signal to noise ratio that big yagi at lower freqs and of course great directivity. Impedance is as computer predicted at <2:1 due to higher impedance openwire feeder to eliminate water accumulating between the conductors. The output of this antenna is split or switched to drive the filter/preamplifier/R8500 and the noise cancelling receiver. It's a great ant with multiple uses for us one tower guys. A separate low power T-R relay is used to isolate the output of this antenna when transmitting on the 8 element yagi.
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Open wire feeder made from UT141 semidrigid coax, only the outer conductor is used, spaced .150 inches. This is greater impedance than the 80 Ohms so it won't collect water between the conductors. It is important to maintain the air dielectric. Delrin spacers are used throughout. Balun is ferrite beads on outside of coax held in place with shrink tubing.
6 element , 24 foot boom, 12.1 dBi design used for Es:
Units=inches, .250" dia elements thru the boom insulated, 1.0"
diameter with.125 wall center section and all others .062 wall. Add
5.1% boom diameter to element length.Tee match, 1.150" spacing, .250"
diameter bars, length = 14 inches each side, fed with half wave
length coaxial cable balun, RG142.
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4 element , 15 foot boom, 10.8 dbi gain, designed for light weight portable antenna. Clean pattern: all lobes >-21 db. Usually run on 21 foot mast. Boom = 1.0 inch diameter with .062 wall. .250 diameter elements with .049 wall. Thru the boom insulated elements in table above already have add 5.1% diameter of boom (.050 inches) added to element lengths.Tee match: .250 diameter rods, 1.0 inch spacing, 12.75 inch length on each side from boom center with 1.625 inches protruding beyond shorts. Shorts are made from 1/4 x 1/2 inch copper bar. RG142 half wave length coaxial balun. Antenna picks up 1 db gain over the shorter boom 12 footer. This one built with splice at the driven element for easy assembly while portable.
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3 element, 5.2 foot boom, designed for super clean pattern (side lobes> -29 dBc) and low gain! Antenna used for 50 MHz noise cancelling receiver. Half wavelength coaxial balun, RG -142. Units=inches, .250" dia elements thru the boom insulated, 1.0" diameter boom, add 5.1% boom diameter to element length. Tee match 1.0"spacing, .250" diameter bars, length = 11 inches each side, fed with half wave length coaxial cable balun.
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Radio:
Homebrew hi level transverter, Rx filtered for 50 to 51 MHz pass band, -45 dBc at 54 MHz, noise cancelling input, adjustable phase & gain. 22 dB conversion gain, 2.5 dB noise figure. Terminating low pass filters on Tx.
Incorporating a FT1000D modified for use as the primary 50 MHz IF radio. TS930 had more than 60 thousand hours of six meter operation on it. (tired). First IF filters need to be added to FT1000D.and similar to 930 transverter mods need to be incorporated but I am finally using it. Going to add a new 8 pole first IF filter, PIN atten and hi level bipolar first IF amplifier replacing the original dual gate mosfet aa 73 MHz.
Icom R8500 receiver used for band segment scanning and third receive frequency. Adding a 43 to 51 MHz "MUF" antenna (above) to drive a 5 pole band pass filter and hi level preamplifier and splitter which will become the "extra" input for several uses in near future. Design will appear under application notes.
3CX800 amplifier, homebrew, 1200 Watts (+60.8 dbm +/- 0.02 db) output at 1 dB output compression point (CW mode). Modifying a TL922A amplifier for "instant on" six meter amplifier.
90 feet of 7/8 inch hardline & 85 feet of 0.5 inch hardline to antenna feed point