Wednesday, October 26, 2016

Antenna Work - Fan Dipole + 80m Marconi

Have been string up support ropes in the trees to get a couple of new antennas up before Winter sets in.   First is the 40, 30. 17 and 10m fan dipole and second its an 80m vertical.

Came across this interesting tidbit on using 2 80 dipole and phasing them together.  Original article here ... http://www.qrz.com/db/VA2GU/?dxc=1


80M LOW WIRE ANTENNAS FOR DXING
This section will show you can also dx, by merely using 20ft high trees/poles for supports.
Also below, i will show you how to use your 4 vert supports of a 4 square to get greater gain and lower angles than a 4 square; all this:
  • without radials
  • without phasing Comtek box
  • without special lengths coax

80M DX WITH "LOW" WIRE ANTENNAS (LOW MEANING 7M/20FT HIGH)
=============================================================


So what is your excuse for not doing dx on 80m?
If you only have low trees that will be just fine!
A simple dipole will just warm up the clouds, but phasing two of them will get you a lot of dx; i mean over 4000 miles/6500km.

PHASING IS NOT MAGIC AND VERY EASY TO IMPLEMENT. NO FORMULAS TO CALCULATE AND NO PHASING NETWORKS REQUIRED. YOU ONLY REQUIRE A TOTAL OF ABOUT ONE WAVE (260FT/80M) ANTENNA WIRE AND 1 1/4 WAVE (325FT/100M)COAX.

1. SELECT 4 TREES/SUPPORTS (20FT/7M WILL DO NICELY) TO PUT UP TWO HALF WAVE DIPOLES
(note: if your wires will be rubbing on tree branches, use Flexweave or other insulated stranded wires; if you use copperweld
DO NOT USE THE STRANDED TYPE; THE INDIVIDUAL STRANDS WILL RUB ON EACH OTHER IN THE WIND, AND TAKE OFF THE LITTLE COPPER COATING THERE IS; CONDUCTIVITY WILL GO BAD, IT WILL THEN RUST AND BREAK).

2. SEPARATE THE TWO DIPOLES BY MINIMUM 35FT(11M), MAXIMUM 70 FEET(20M). (note: this will affect only the f/b mostly. Max gain is at the higher separation, max f/b at the min.)

3. TRY TO TUNE EACH DIPOLE alone TO RESONATE AT THE QRG YOU WANT.

4. USE A CURRENT CHOKE AT THE ANTENNA, (you can make one by winding 8 to 10 turns of coax 8 inches(20cm) in diameter)

5. FEED EACH DIPOLE TO THE SHACK USING 1/2 WAVE OR MULTIPLES OF 1/2 WAVE COAX: about 90 to 110 ft depending on the VF of your coax (this includes the coax you use to make that current choke)

6. IN THE SHACK, JOIN THOSE TWO COAX ENDS WITH A SIMPLE "T" FITTING; BUT.....

7. NOW THE TRICK IS TO PHASE THOSE TWO DIPOLES; SIMPLE. CUT A LENGTH OF COAX ABOUT 130DEGREES (70FT) AND INSERT THAT COAX PIECE IN SERIES BETWEEN THE "T" AND THE COAX GOING TO THE ANTENNA WHICH IS CLOSER TO THE DX YOU WANT TO WORK.
(note: this coax phasing line should theoretically be 90 degrees; but i find 120-130 degrees gives me max. gain)

8. NOW IF YOU WANT TO REVERSE DIRECTION, SWITCH THAT PHASING LINE TO INSERT IT IN THE OTHER END OF THE "T" GOING TO THE OTHER ANTENNA.
(note: i use a cheap knife switch to change directions fast and check f/b easily)

Here below are the AZIMUTH/ELEVATION graphs showing the differences in the gain and elevation angles between your cloud warmer (simple dipole) and the phased array (phased array may sound like impressive words; but they only mean two pieces of wires (antenna) connected by 2 different lengths of coax...)

You can see a 5 db difference FROM 2.5 DEGREES TO 30 DEGREES (YES I MEAN 2.5 DEGREES!) ; this may not get you a booming sigs in JA/VK, but sure to get you strong rx dx sigs and be heard by those your hear.


Wednesday, October 12, 2016

Log book update

Its been awhile since I did much with the radio but thats the was Summer goes.    Working on getting 3 Antennas built before the snow flys my Fan Dipole and an 80m and 160m vert.     The sw box is all installed up the hill.   I recently dropped a bunch of trees to make way for the dipole ... verts are allot easier!   The fan dipole is more or less ready to be strung up as soon as I clear away a bit of the trees that I dropped.    

Worked a few on 40 a couple of weeks ago...cool!   This is my log book update....