Why Full Power is Good!

August 29, 2014

matching_network

Full power forces you to make sure that everything in the chain between the exciter and the antenna are working 100%. No bad solder connections, no wimpy under powered chokes or baluns, no antenna tuners that are not up to the task. This is especially true on 160M – trying to get full power on Top Band will really “test your mettle”, especially with the shortened antennas that most of us are forced to build. As you go up in the bands and you can put up 1/4 w.l verticals or full sized yagis – that do not have traps or other coils and whatnot – then the situation gets a lot better. The circuit is from page 9-42 from the ON4UN Low Band DX-ing Book – but modified for the exact components and values that I used, as well as the height dimensions:

ky6r_match

What is especially nice is that I can tune this circuit for 160M and 80M and bypass the Palstar AT2K – which – like most tuners – cannot handle 160M at all – and can barely handle 80M – especially at full power. The key was to BYPASS the AT2K – because it had arc’ed on the lowbands before with its components switched in. My KAT-500 with the KPA-500 did a better job – but that’s because that was a switched L circuit – not a T circuit.

I remember the Ten Tec 238B – for 160M – they gave you extra capacitors, and I feel that’s almost kind of “hokey” – and that its much easier to resolve these issues at the base of the vertical – not back in the shack. But as always – I am learning.

I will do some more research, but it seems that I can come up with a tuned circuit and switching arrangement than can handle the power on 160M and 80M and just switch between 160 and 80M.

One really nice thing – I have several high voltage rated capacitors, including this bad boy – the Palstar BT-1500A:

Palstar BT-1500A inside

And I even have those roller inductors, so – I will be having fun coming up with a switched and tuned circuit for 160 and 80M – that won’t arc. I can’t do any better as far as the vertical itself goes – and it is quite a bit improved over the MA-160V that it replaced, but on a small lot – this is considered a pretty nice little lowband antenna system.

The resonant frequency of the vertical – with no components in line – is 3.1 mhz – so it “splits the difference”.

My antennas on 30, 40, 20 and 15M are also either at resonance and don’t require a tuner – or require so little from the tuner that it doesn’t matter.

And the fact that 160, 80, 30, 40, 20 and 15M can handle full power is the real test!

 

 

FT4TA and KY6R on 15M

August 29, 2014

ft4ta_ky6r_15M

After assembling the homebrewed 15M yagi, I realized that it would overlap underneath the 3L 20M yagi more than I would have liked – and could cause some negative interaction. It also was heavier and might be a bit too big for the support mast that I have.

I was wondering if just using my 3L 20M yagi as a rotatable dipole on 17 – 10M would be “good enough”. Its not – see the blue line. However, a lightweight wire Moxon could be a great solution (red line). The 3L yagi would be 1.5 dB better than the Moxon, and the Moxon is 2 dB better than the rotatable dipole idea. So its a great compromise.

ft4ta_k6tu

15 meters is a good band to add a monobander to – because we are still in the same year as the peak of Cycle 24. When VK0EK goes to Heard Island, 17M will be the better of the two bands to put something up – and I will no doubt swap the 15M Moxon for a 17M Moxon next year.

I tweaked the tuning on my 160M short hatted vertical and can now run legal limit on it, but I will still probably keep it down to about 1KW just to be safe. On 160M – when you have a short hatted and loaded vertical – the voltages are so high that all kinds of weird arcing can happen – so its better to play it safe.

mox_ss

So, with this 15M Moxon, I will have mono banders on 160, 40, 20 and 15, and can run legal limit on those bands. I can run 200 watts easily on 30M with the tuner, and will be able to use either the yagi or the Moxon on 17M with a tuner. I am not going to worry about 80, 12 or 10M so much, but with a tuner can also use those bands if necessary.

RatPakSystem

On a scale of 5, I give the Array Solutions Rat Pack remote antenna switch a 10. I also give the Array Solutions Stack Match II switch a 10. They are very well made – when you look inside, you get a very strong sense of confidence that these switches will handle legal limit and more.

default

I have used lesser brands – and they were no where near up to the task like the Array Solutions products are. I also had the Array Solutions K9AY Loop System, and that was also superb.

I’m a very loyal customer, and Bob, Jay and David have always done right by me. I will be a “repeat offender” at Array Solutions!

More Antenna “Thinking”

August 26, 2014

ant

My 20M 3L full sized yagi is a keeper. It is up 45′ now, and in a couple weeks will go up to 55′.

cap_hat_vert

My 160 / 80M low band shortened (but optimized) top loaded and hatted vertical is a keeper.

Now – here’s the big question. For 40M I used a phased vertical array, and I also can use this same array on 30M and it works quite well. Here is what EZNec says about the gain at several takeoff angles:

DEGREES                         GAIN(dBi)

15                                        1.94

20                                       2.71

25                                       2.95

35                                       2.65

And now – if I were to put a 40/30M rotatable dipole up above my 20M 3L yagi at 55′ – on 40M:

DEGREES                         GAIN(dBi)

15                                        2.83

20                                       4.61

25                                       5.68

35                                       6.46

And on 30M:

15                                        6.86

20                                       8.0

25                                       8.39

35                                       6.95

When I modeled the 15M full sized yagi with all other antennas, I found it would degrade and cause negative interaction with my 20M 3L yagi – so I just can’t do that. While disassembling that yagi – I looked through my aluminum pile and found that I can easily build something very much like the Optibeam 40/30M rotatable dipole – that sells for something like $700, but do it with my own aluminum – where I already have the elements almost done.

In fact, I could then take down the phased vertical array leaving two antennas up – and with basically NO negative interaction. I would end up with the 3L 20M yagi with the 40/30M rotatable dipole above it – and each antenna would have their own feed line. Then I would have the 160 / 80M vertical.

I would then have very good small lot antennas on 160, 80, 40, 30 and 20M. The 20M 3L goes into the AT2K “Bypass” port, and the other two feed lines go into the two AT2K antenna ports.

I would forgo the gain on 15M but pick it up on 30M, and I am OK with this since we will be going down the cycle in the next few years. And I think between the rotatable dipole up 55′ and the driven element of the yagi – I would be “OK” on 17 and 15M. I don’t care about 12 and 10M, so they aren’t a concern.

 

 

15 Meter Yagi Feed

August 25, 2014

IMAG1100

I’m building the hairpin match and adding the 1:1 current choke for my 15M yagi. With the driven element on saw horses, the resonant frequency with a 1.1:1 SWR is 20.625 mhz.

15M_hair

YW said that the hairpin should be 13.8 inches, and that is about what it is in real life. I have trimmed the hairpin rods back to something in the 16″ vacinity since I took this picture.

I do know that the effect of having the driven element so close to ground means that the resonant frequency will show about 200 khz low.

My next test will be to add the director and reflector and re-check the tuning. It will be interesting to see how the “interaction” between elements affects resonant frequency – if at all. I am guessing that all of the tips need trimming, but I will test tomorrow and see for sure. Maybe just the driver needed trimming?

IMAG1102

The mechanical aspects of this make the project challenging and fun. Here is how the W2FMI 1:1 current choke is connected:

IMAG1103

There is about 1 inch of very heavy 8 guage copper grounding wire going from the elements to the choke. These heavy wires also act to anchor the choke down onto the boom. I will secure the balun and it will be further reinforced by the way I connect and tape the coax feed to the boom. I do wonder if that inch of wire extends the driver size – and hence why trimming about 3″ was need (?). Seems reasonable.

So – after I assemble the entire yagi and re-tune, I will report back. I’m hoping to get the resonant frequency tuned (on saw horses) at about 21.000 khz, because then it will be centered between those parts of the CW and SSB bands that I will operate in about 21.200 mhz.

[UPDATE]

I added the reflector and director and the resonant frequency changed upward – from 21.625 to 21.750. The SWR is a little higher – 1.2:1 instead of 1.2:1 – but I did not retweak the hairpin match.

YW is quite “close”, but you do have to tune and tweak a bit. YW gets you in the ballpark for sure.

ACOM 1500 Online!

August 23, 2014

acom1500

The ACOM 1500 is in line and on line now. Its a beauty, and is so simple and fast to tune (fool proof) that I see no need for an autotune amplifier. It only takes seconds to tune and the TRI circuit and protection circuits seem to be very good at preventing tube damage from mis tuning. Another nice feature is the way you can tune to any power level without following some “special” tuning method. This means if I want to go with just 1000 watts – I will. I will most likley reserve 1500 watts for the pileups and for the tougher 160M QSO’s. I do want to be careful not to get into my neighbors stereo as I did years ago when I had a Ten Tec Titan III amp. This time round, my antennas are higher and have much better chokes at the feed points. Back then, I had a Moxon only up 30′ and with basically no choke at the feedpoint. A few beads around the coax just didn’t cut it.

The shack is now quite simple and straight forward, yet effective. This week I will receive and install the Array Solutions Ratpack, and then I can add the 15M monoband yagi – which I’m putting up just for FT4TA.

ahr

This is a very interesting discussion. I appreciate everyone’s view points – and pretty much agree with parts of what everyone is saying. I’ve been thinking about this a lot more than I expected to.

I also think we are just talking about the ARRL DXCC Program, and specifically Honor Roll, and Honor Roll #1.

Since there is absolutley no way to enforce any kind of distance limit, I think we end up relying on the Honor System. I think we have been relying on the Honor System since day one anyway – since there are so many ways one can have more than just a “propagational advantage”. I talked to a card checker once who told me stories about “card cheating” – especially the tricks some play with 160M cards. So – the program has already had many challenges to maintain its integrity. I think changing the rules as they had done in years past was actually the biggest threat to the program. There are some pretty “heated” stories about rule changes that gave advantages to some. Glad those days seem to be over.

None of the proposal or discussion has raised my blood pressure one IOTA (cymbal crash!), because if anyone even cares to bother and look at my QRZ.COM page – looking for call signs they see on the DXCC Online List or Clublog “Leagues” or whatever, they will see my “disclaimer” about how I achieved my “award levels”. Thats good enough for me – that alleviates any and all concern about HOW I did it vs. how others do it. Its my “bragging rights” – and those who like to build their own antennas are the (only) ones who actually talk to me at club meetings.

As much as I love the DXCC Program, I have my “pet peeves” as well – especially why this or that entity is on the list. Its really trivially silly good fun. Its also not the only “operating activity” that I particpate in – but is the only “organized” one that I do. I am not a contester and don’t chase any other “operating activities”. Some other “operating activities” are actually a lot more diffcult than DXCC – in all its flavors, but for me its only DXCC as far as that “awards” go. I think it is the “legends and lore” that keep me interested.

There are other “propagational advantages” that I have no control over. The guys who can afford to live on the hill tops in Orinda have an amazingly better “propagational advantage” than I do down in the bowl (living in a van, down by the river, eating Government Cheese).
And until a “life changing event” that happened 9 years ago – I used to live on 5 acres just about on top of a ridge in Lafayette – between Burton Valley to Rossmoor. I worked my entire life to get there – and with one email message – it was gone. Life changes happen – usually faster and more unexpectedly than you’d wish.

In fact, the award means a lot more to me because I had to work harder in a compromised location and also because I added my own “rules” on top of the ARRL DXCC rules. I kept my power down to 200 watts or less and wire for the first 300, then I changed my rules and said 500 watts was OK – and aluminum is nice. Now that I can finally hear all those stations I missed with low wires, I have decided a nice ACOM 1500 would look great in the shack. The shack colors were somewhat “drab” and I couldn’t have that . . . I mean what would the neighbors think?

See – its a game. I change my own rules that affect my challenge or pursuit MUCH more than worrying about someone else using a remote or whatever. I’m worrying more about running HFTA and K6TU’s propagation service with my Antenna.13 file to make sure I have done everything possible to work FT4TA and VK0EK – and then be only 6 away from Honor Roll #1. I’m “remote agnostic”.

Do I care how others do it? No – but I love hearing your stories – and realize the only worth of the “award” is the bragging rights we get. In fact – the biggest part of the program that excites me is hearing how you did it. If you say you were travelling on business and used remote stations – I will be really intersted to know if you used one of those cool Elecraft remote control head thingies . . . . I’ll be interested in latency. I’ll wait for the day where someone complains that they couldn’t get on the only station that gave them the “best chance” because someone else had hogged that remote station. Maybe it will even show up in the cluster spots. Speaking of that – some have denounced the cluster as the end of “real DX-ing”. I know of a guy who refuses to upgrade to Extra from Advanced because he “did it the old hard way”. We all have our DXCC Crosses to Bear.

The DXCC Honor Roll Plaque – when I carried it down to Peets Coffee did not impress the “barrista” enough to even give me a free cup of coffee . . . in fact, they asked me to kindly leave their fine establishment. I think it was my orange safety vest with my call letters and big baseball cap with letters on it that really scared them. Or maybe how I seemed to be “listing” to one side as I ambled in through the door and yelling at the top of my lungs “I made the grade, I MADE the grade” . . . .

So – what is my idea of a great solution?

NO mileage constraint or rule – instead – add another “mode”. After all – satellites are really “remote operations” from the sky!

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