Sunday, May 22, 2016

20 Meter 5/8 works??????

OK ,  put one heck of and effort into the 20m 5/8 last summer only to determine that it really wasnt working all that well.    Just for the heck of it I heard a guy calling in Bulgaria ,  on RX 5/8 was S7 on the 1/4 S6 so I gave him a call and got a 599 back....well it was a 599 that probably was a stretch!    Best thing is this antenna at 14.0 Mhz has a VSWR of 1.1:1.  

20m 1/4 gp tuning

Checked using the vswr meter on the radio ....

Initial ....

14.0    1.6:1
14.1    1.5:1
14.2    1.4:1
14.3    1.4:1
14.4    1.4:1
14.5    1.6:1

Going to #1 add to the vertical element 18" to drop the VSWR aiming for 14.0 @ 1.4:1 then #2 I am going to add another 8 radials and see if I can get the VSWR down further.  

With the added 18"

13.9    1.8
14.0    1.6
14.1    1.6
14.2    1.6
14.3    1.7
14.4    2:1  

So no doubt the optimum is lower but the overall VSWR is suffering.  So now its about the radials .....

Friday, May 20, 2016

Antenna season is here ... I have a plan!

 I have been gathering stuff for some upcoming antenna projects and have been doing lots of reading and have a plan!  

Phase A ... top of hill

   Over the past couple of days I have installed another RCS4 Antenna Switcher at the top of my hill.   Currently there is a 14avq feed by 500 ft of mostly heliax.....very low loss!    The 14 avq continues to perform very well on 40, 20 and 15 meters often outperforming my 40 and 20 m 1/4 GPs.    So I now have 3 antennas to build at the top of the hill....

1 ) Fan Dipole 40, 30, 17, 10 and 6 meters.    Should be up high enough for a low throw on 40m...other bands are no problem height wise.    6 mertes is a first and the 10 meter is a 14avq replacement for some reason 10 on the avq sucks.

2)   80m 1/4 GP with 8 radials to start.   I currently have a skywarmer in the form of a 80m dipole too too low to the ground!   Once the 80m vert is up the dipole will be trashed.

3)   30m 1/4 GP the same as what I have next to the house.   This will be my height advantage test ....nearly 100ft more in elevation.  

4)  Wouldn't mind trying some "tuned radials on the 14 avq ... I know I can do better with the ground plane.  

Phase B... just behind house

 1)  Last summer I built a 20m 5/8 that didn't cut it so its going to be scrapped.   In its place a 160m 1/4 GP with 8 radials.

2)  Going to re-purpose the 8 radials from the 20m 5/8 and add them to the 20m 1/4 gp for a total of 16 radials.  

Phase C ....  at the house

1 ) Don't have anything for 2m so I have a spare 5/8 I am going to mount in place of  the KA Sat Dish.  Primarily to monitor a couple of local FM Repeaters and 52 when in the shack.  

 I am sure I will come up with a few other plans however the above will probably take me into the fall.  What I will end up with is a new capability on the 1.8 and 3.5 MHz!  

 Antennas I will end up with ......

2 Meters-  5/8 Vert
6 Meters -   High Dipole
10 Meters -  14avq very ( so so ) and Dipole
15 Meters - 14avq very good results with this antenna on this band
17 Meters - 1/4 GP Vert very good reults with this antenna dead flat 1:1 VSWR and Dipole
20 Meters - 14avq Vertical,  1/4 GP Vert  jurys out on theses two ... both performers!
30 Meters - Dipole and 1/4 GP Vert very good reults with this antenna dead flat 1:1 VSWR
40 Meters - 14avq ,  1/4 GP Vert and Dipole
80 Meters - 1/4 GP Vert
160 Meters - 1/4 GP Vert

Beverage notes ...

Greta blog post on building the matching transformer for a beverage antenna ...

Thursday, May 19, 2016

Some fan dipole thoughts ...

They found that the wires at the center feed point had to be separated by at least 5 1/2 inches vertically and the ends separated by 38 inches in the 2 to 18 MHz range. As in any fan dipole construction, all of the dipoles are connected in parallel but in the SRI method, the separation between them at the feed point must be maintained.
By this simple change they found that you could accurately cut the antenna element
lengths for given frequencies and eliminate the need for pruning.

In the drawing above, the lowest frequency antenna is on top and is cut 4% short of the standard 1/2 wave length. (Length in feet= 0.96 times 468 divided by the operating frequency in MHz).

The middle frequency antenna (lower in frequency), is cut for an exact 1/2 wave length. (length in feet= 468 divided by the frequency in MHz)

The highest frequency antenna is at the bottom and cut for 1% longer than the 1/2 wavelength (length in feet= 1.01 times 468 divided by the frequency in MHz)

Compared to the construction effort of a standard multi-band dipole the only difference is the fabrication of a feed block or center insulator that is about 12 inches vertically by 3 inches wide, so make sure this is made of a good insulating material such as Lucite, Bakelite, fiberglass, or PVC. 
The end 38 inches of separation can be maintained by separate halyards on each element or a spreader bar with a common halyard.
The bandwidth will be at least plus or minus 2% for a 1.5 to 1 SWR according to Stanford Research Institute.

(Each leg is shown in length so you will need two legs.)

10 METERS = 8'4"
12 METERS = 9'5"
15 METERS = 11'1"
17 METERS = 12'10"
20 METERS = 16'8"
30 METERS = 23'2"
40 METERS = 32'9"
60 METERS = 43'7"
75 METERS = 60'9"
80 METERS = 65'6"
160 METERS = 123'5"

137 KHZ = 1708'1"

Monday, May 9, 2016

Log Book Update

Didn't thinks I was too busy over the past month and a bit but I still worked a bunch of DX.    There hasn't been quite as much time for the radio with the warmer weather and lots of things on the go.