Tag Archives: Antenna

GAP Titan Antenna – SWR Analysis

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So I have my antenna up and I took the time to run through the SWR charts for all of the bands. I can say it lives up to expectations — it resonates everywhere it was claimed to. I do have a bit of tuning I need to do on 40m and 15m, but both should be easy changes. One is to adjust the counterpoise to be a tad longer to lower the 40m resonance, the other is to slightly lengthen one of the tung rods by clipping on a wire extension.

I did this with about 100′ of LMR-400 equivalent between my meter and the antenna. On 6m it should have less than 1dB loss. Even on the 2m test it’s only at 1.5dB. The readings were similar to what I was seeing when I was out next to the antenna so I’m going to present these numbers since I had the opportunity to take far more readings.

Something to note: three of the bands I’m reporting on are not speced to be any good from GAP. 160m is a dud, but that’s completely expected. 6m and 2m likewise aren’t speced for the antenna but I’m less than 2.0 SWR for half of the 6m band and all of the 2m band for what it’s worth.

SWR is obvious: it’s the standing wave ratio. Rs is the pure resistive resistance and Xs is the reactive resistance. The meter doesn’t specify whether it’s an inductive or capacitive reactance.

Band Frequency SWR Rs Xs
160 1.8 20.1 125 351
1.85 20.4 416 488
1.9 21 254 416
1.95 22 76 258
2 20.7 34 173
80 3.5 5.5 44 115
3.55 5.2 77 132
3.6 4.8 142 128
3.65 4.6 164 92
3.7 3.6 116 84
3.75 3 84 68
3.8 2.4 67 49
3.825 2 63 40
3.85 1.8 61 31
3.9 1.4 65 12
3.95 1.7 79 19
3.976 2 92 30
4 2.5 8 46
40 7 3.2 88 82
7.05 2.7 124 37
7.1 2.2 90 37
7.116 2 79 37
7.15 1.8 58 33
7.2 1.6 41 20
7.25 1.5 34 7
7.3 1.6 31 8
7.35 1.9 31 18
7.385 2 32 25
20 14 1.3 40 10
14.05 1.3 39 8
14.1 1.3 39 7
14.15 1.3 39 6
14.2 1.2 39 5
14.25 1.2 40 3
14.3 1.2 40 2
14.35 1.2 41 1
17 18.068 1.5 32 0
18.118 1.4 34 0
18.168 1.3 37 0
15 21 2.9 72 69
21.05 2.6 95 57
21.1 2.3 108 31
21.15 2 102 13
21.2 1.8 90 17
21.25 1.6 77 19
21.3 1.5 68 14
21.35 1.3 64 11
21.4 1.3 68 5
21.45 1.3 64 6
12 24.890 2 103 4
24.940 1.8 87 18
24.990 1.9 71 21
10 28 1.7 32 14
28.05 1.7 36 17
28.1 1.6 40 19
28.15 1.4 43 23
28.2 1.6 49 24
28.25 1.5 55 23
28.3 1.5 31 21
28.35 1.5 65 18
28.4 1.5 68 14
28.45 1.4 71 9
28.5 1.4 72 2
28.55 1.4 72 0
28.6 1.4 69 7
28.65 1.4 64 13
28.7 1.3 60 15
28.75 1.3 55 15
28.8 1.3 52 15
28.85 1.3 49 14
28.9 1.3 46 13
28.95 1.3 44 11
29 1.2 41 8
29.05 1.2 39 4
29.1 1.2 38 0
29.15 1.2 38 0
29.2 1.2 39 0
29.25 1.2 40 2
29.3 1.2 42 6
29.35 1.2 45 8
29.4 1.2 48 10
29.45 1.2 51 11
29.5 1.2 55 11
29.55 2 59 9
29.6 1.3 64 6
29.65 1.3 67 1
29.7 1.3 69 0
6 50 2.3 34 33
50.1 2.4 27 25
50.2 2.4 23 16
50.3 2.3 27 7
50.4 2.3 20 0
50.5 2.3 21 4
50.6 2.2 25 13
50.7 2.2 30 21
50.8 2.2 40 32
50.9 2.2 58 40
51 2.2 90 38
51.1 2.3 110 23
51.2 2.4 111 24
51.3 2.5 84 50
51.4 2.5 59 50
51.5 2.6 39 39
51.6 2.6 31 31
51.7 2.6 24 21
51.8 2.5 21 11
51.9 2.5 20 5
52 2.4 20 3
52.1 2.3 23 11
52.2 2.2 29 20
52.3 2.1 39 30
52.4 2 54 36
52.5 2 78 33
52.6 1.9 97 10
52.7 1.9 89 21
52.8 1.8 67 32
52.9 1.7 50 29
53 1.6 42 23
53.1 1.5 37 15
53.2 1.4 36 5
53.3 1.2 37 0
53.4 1.1 41 0
53.5 1 46 0
53.6000000000001 1 50 0
53.7000000000001 1 52 1
53.8000000000001 1.1 51 5
53.9000000000001 1.2 47 9
54.0000000000001 1.2 43 8
2 144 1.8 27 6
144.2 1.6 30 0
144.4 1.4 37 11
144.6 1.3 55 16
144.8 1.7 73 0
145 1.6 70 21
145.2 1.8 50 33
145.4 2 35 27
145.6 2 27 18
145.8 2 25 8
146 1.8 26 0
146.2 1.6 32 7
146.4 1.5 42 17
146.6 1.4 61 15
146.8 1.4 72 0
147 1.5 62 19
147.2 1.6 46 23
147.4 1.6 36 19
147.6 1.7 31 12
147.8 1.6 30 2
148 1.5 32 0

 

Overheard while putting up an antenna – or – That’s what she said!

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Why don’t you come over and look how long it is. It’s hard to imagine it fit in that small box!

Can you feel it?
No.
I’ll wiggle it for you.

Can you feel me?
I feel you! I Feel you!

I guess I have to use the three big holes.

The guys don’t have to be that tight… just keep it from whipping around.

Pull it out real slowly.

I’m coming out of the closet.

Oh — that’s a long rod.

I’m just going to pound that rod in.

Let me know when you need another napkin.

Ok pull it… slow down!

Let me see if I could shift it over a bit.

- = -

And not one of these is what you think.  Razz

SWR Analysis – MFJ-269 Antenna Analyzer + Comet GP 15 Antenna

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Earlier in the year I wired up a Comet GP15 antenna in my attic. Yesterday I finally had a chance to test it!

It’s nice being able to peer inside what seems like such a closed system: an antenna and a feedline.

In my tests I had around 60 feet of feedline between me and the antenna, but in the few spot tests I’ve done the feedline doesn’t seem to affect things very much. I’m using very low loss LMR-400 coax to hook things up and it’s some top-shelf stuff.

The box itself is around 4x7x2.5 inches around (not counting the antenna socket and the knobs) It has a very simple interface — you dial in the frequency and it tells you about what it sees.

It give you a lot more than just the standing wave ratio (SWR) of the system, it breaks it down by te resistive load versus the reactive load. It doesn’t go so far as to tell you if it’s a capacitive or a inductive load, but you can figure that out by sweeping the frequency around a bit. It doesn’t have the capabilities of a $20K network analyzer, but it’s a good product for what you’re paying for it.

Overall I found that the antenna is quite good in 2m and 70cm, but it’s just not all that on 6m.

 

6 Meter
Frequency SWR Rs Xs
50.0 4.0 56 69
50.2 3.6 39 54
50.4 3.4 28 42
50.6 3.2 22 32
50.8 2.9 20 23
51.0 2.5 19 16
51.2 2.2 21 7
51.4 1.9 25 0
51.6 1.5 31 4
51.8 1.2 41 8
52.0 1.0 50 3
52.2 1.1 53 5
52.4 1.3 49 12
52.6 1.4 41 15
52.8 1.6 35 14
53.0 1.7 30 12
53.2 1.9 26 7
53.4 2.1 23 1
53.6 2.2 22 3
53.8 2.4 20 5
54.0 2.7 20 9

 

 

2 Meter
Frequency SWR Rs Xs
144.0 1.6 46 24
144.2 1.6 42 21
144.4 1.5 39 17
144.6 1.5 37 13
144.8 1.4 37 10
145.0 1.3 38 7
145.2 1.2 39 4
145.4 1.2 41 3
145.6 1.1 45 3
145.8 1.0 48 3
146.0 1.0 51 3
146.2 1.1 52 5
146.4 1.1 52 8
146.6 1.2 51 11
146.8 1.2 48 14
147.0 1.4 44 16
147.2 1.5 40 16
147.4 1.5 37 15
147.6 1.6 34 13
147.8 1.6 32 11
148.0 1.7 30 7

 

 

 

440 Mhz
Frequency SWR
420 1.9
420.5 1.7
421 1.5
421.5 1.3
422 1.1
422.5 1.3
423 1.5
423.5 1.9
424 2.1
424.5 2.2
425 2.1
425.5 2
426 1.7
426.5 1.4
427 1.2
427.5 1.3
428 1.6
428.5 1.9
429 2.0
429.5 2.2
430 2.1
430.5 2.0
431 1.7
431.5 1.4
432 1.2
432.5 1.2
433 1.4
433.5 1.7
434 1.8
434.5 1.9
435 1.9
435.5 1.8
436 1.6
436.5 1.4
437 1.2
437.5 1.1
438 1.2
438.5 1.4
439 1.5
439.5 1.6
440 1.5
440.5 1.5
441 1.4
441.5 1.3
442 1.4
442.5 1.4
443 1.5
443.5 1.5
444 1.4
444.5 1.3
445 1.1
445.5 1.1
446 1.3
446.5 1.5
447 1.7
447.5 1.8
448 1.7
448.5 1.8
449 1.7
449.5 1.5
450 1.2

 

 

 

 

Putting up the antenna – Part 1

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We made it past a major milestone last night: we have a way of getting the antenna feedline out of the house!

This was a harder job than I expected.

Maybe it’s because I never did it.

Let’s take a step back though. My station is located next to my computer in my office on the second floor of my house.

The top right window belongs to the room.

I could have done the simple thing and that’s go up to the attic then down the wall to the basement in an existing wire run I have… but that would add another roughly 20 feet to the cable run. That’s bad for a couple of reasons: 1) more attenuation of the signal 2) longer ground run means more potential for noise.

The solution I crafted was to punch through the footer of the second floor in the bedroom closet, make a hole in the first floor footer from the basement and fish it down the wall.

That was the easy part.

The hole in the basement took a brand new right angle drill to make.

The furthest hole is the right one.

Well, maybe.

Fishing from the top we couldn’t get through. Nor from the bottom. Fishing from both sides we were able to make them clink together, but never could make them come through.

Grrr…

Ok. So yesterday I was hanging out in the new office waiting for a package that never came. I was hanging out with the electrician who was wiring the place up so I asked him what the trick was. Scott told me the trick of cutting a blank outlet out of the wall to get access to it — when you’re done just slap on the blank cover and it’s as if you were never there.

Ok. So after I got back I cut the hole in the living room.

(Ok, so it’s taped up to keep the kitties out)

No joy in getting into the hold I drilled out. Dammit.

Ok. Let’s try out the new flexible drill I picked up. Now I was aiming to go further back than the two wires.

Drill. Hit something hard. Drill. hit something hard.

“En, do you see me coming out in the basement?”
“No. But I smell you.”

Drill. Come out the the other end.

“Do you see anything now?”
“No.”

Ummm… where did I just come out.

I walk around and see this:

(Well, I see the drill, not the string I put in later.)

Sigh… I guess the hard I was hitting was the bricks. I now know how not to use the flex drill. I think I can intuit the rest now. heh. Thinking

I need to get the feedline and ground out anyway. This is even more direct. I guess.

All I need now is the ground rod and I’ll be set! I need one more hole in the side of the house to bond the ground rod with the rest of the house ground. I know where to put that one though — right next to the phone entry — and it’s not awkard to get to in any way. Grin

Some time over the weekend I can finish up:

  • Pull the coax and ground braid outside
  • Cover the hole in the living room
  • Pound in the ground rod
  • Affix the lightning arrestor to the ground system
  • Bond the new ground and the house ground
  • Solder up connectors on the coax
  • Erect the antenna
  • Test
  • Waterproof the wiring
  • Caulk the antenna exit hole
Then I’ll be on the air!