August 25, 2016
The best thing about experimenting in your own back yard is that you can take your time, play around and just have fun. I have a world of adventure right here in the shack and in the backyard. This is the best antidote to frustrations at work – where our office just moved from one of the best parts of San Francisco to one of the worst – with the worst commute I have ever had. Thank God for Ham Radio and these low band RX antenna projects!
I was going to circumvent putting up the K6SE Diamond loop – because I had expected to get right to the Christman fed 80M Full Wave “broken” Delta Loop – which is now a pair of linear loaded 160M verticals. BUT, I won’t be getting my DX Engineering RG8X coax crimping tool or special crimp connectors until early next week, so, this means I have a weekend to play with something else, and because I already have built the K6SE feed transformer
and terminating resistor
Why not? I will then be able to A-B test it against the MA160V, the linear loaded vertical and the 3 loop phased RX array. Its especially easy because I will using the Ameritron RCS-4V to remotely switch between the center coax loop and the K6SE:
I show the Stackmatch II in this diagram – but its really the RCS-4V. The aperture of the K6SE loop is so much larger than the coax loop – I expect that it will be better, and that phasing it with 2 other coax loops using the MFJ-1025 and NCC-1 will be an eye opener. Then, I will do a “shootout” between the K6SE in this configuration and the Christman phased linear loaded wire verticals.
Speaking of that – when I do get my crimper next week – then I will cut the RG8X into these lengths:
71 degree phasing line @ 82 velocity factor – 87.207 feet
84 degree lines – 103.174 feet
But, first things first. I want to be methodical and do as much A-B testing since this will inform all future RX antenna solutions. I’m still betting on this final antenna combo that will last up until I make Top of Honor Roll:
DXU-32 – 40, 30 and 20M (yes, it doesn’t make sense to turn it into a Waller Flag just yet – but certainly in the future)
Phased wire verticals on 160 and 80M. I killed my 80M abilities when I broke the 80M Full Wave Delta loop – so now I need to fix that. I have enough coax now to actually create phasing lines for 80M, and which can just be manually swapped at the base of the antenna:
71 degree – 45.318
84 degree – 53.615
I will also wire up the Stackmatch II control box. Lots to do and big fun ahead in antennalandia.
August 25, 2016
The Cushcraft MA150V is rumored to have been designed by Joe Resisert, W1JR. For a 36′ top loaded 1/16 wavelength antenna on Top Band, its nothing short of amazing. (Bad pun intended).
The double wire vertical idea is basically two linear loaded verticals spaced 1/8th wavelength apart, which is 70′. They are full sized 1/4 wavelength verticals, and their resonant frequency and SWR are in the range of where a Christman feed will work very well – I will get the F/B, but not much gain. What I will get is no loss, and I am sure the MA160V is maybe 50% efficient. I think the linear loaded full wave wires will be more efficient – more than 50%, but according to the ON4UN Lowband DX-ing Book – page 9-46, probably about 62 – 65% efficient – just for one vertical. When they are phased – I don’t know how this is affected.
But the fact that I worked FT5ZM and VK0EK using the MA160V still amazes me – these two 10K plus distance QSO’s on Top Band are by far achievements that easily surpass all others. I did not have a good RX antenna at the time – but even hearing the few beeps and boops that I did on this short antenna is pretty crazy. On TX – its just fine.
I have two posts at 35′, and have thought about phasing two MA160V’s – but I think that’s a bridge too far and self defeating. It is very possible that the phased wire verticals will beat the MA160V, but since I have been doing so many tests where the goal is to beat the MA160V – that speaks volumes of what a great antenna this is.
I have no idea why DX-peditions don’t use these.
August 24, 2016
Today I will feed both halves as a weird dipole and compare against what I saw yesterday. I am most curious to see if two “prongs” are better than the MA160V vertical. In some ways I have a hard time believing the EZNec model that shows a 20 degree takeoff and the directivity that its suggests. I think a dipole feed actually should end up looking like a vertical and maybe with a high take off angle.
In fact, the model I have been touting is accurate for a Christman Feed, but not as a dipole. And that’s OK – because the Christman Feed is what I ultimately want.
As soon as I get home from work I will correct the model and post it here:
OK – that makes more sense. The loss is terrible on Top Band.
Yes – a dipole pattern – the deep nulls are probably because of the feed being so low. I’m surprised that the takeoff angle is as low as it is, and one thing for sure – the old 80M Full Wave Delta loop no longer performs well on 80M – at least not for local signals. The MA160V with some reference stations on at night was S9 +20 dB, and the dipole is S9 +10 dB – but it is MUCH quieter – much less noise. So – single verticals phased is the right answer, and I expect that end fire and broadside will be noticeable and maybe a lot quieter than the MA160V – that’s my guess from these experiments.
We do know that as a dipole feed the SWR looks like this:
One great thing – with no stations transmitting, the dipole is 1 S Unit quieter than the 3 loop RX system – so that’s pretty important.
But the resonant frequency is what counts only with the Christman Feed, and so I probably should also test the “other side” with the antenna analyzer, and I will post it here:
This is really great – I add just a few feet of wire on the North – it will be tuned to match the south slanting vertical. This means a Christman Feed will work – but the phasing lines will be long. That’s why that 500′ spool of RG8X from VK0IR and VK0EK will come in handly – unless I tried a phasing box of some sort – but they are very expensive – too expensive for something that might not turn out. Actually, the two element phasing box by DX Engineering is priced very reasonably:
At $450, that’s in my budget . . . hmmmmmm. The problem is whether or not the wire verticals with such severe linear loading and with the tips of the wire 2 feet apart would obviate the cost of such a switch. Cutting three coax phasing lines is dirt cheap in comparison. But the lines will be long and have to be coiled up. I wonder how much that affects the system . .
August 24, 2016
With both legs (halves) of this now “broken” delta loop fed at the bottom, the SWR is higher than the 160M band, and very narrow banded:
But, it gets a lot more exciting when you feed half of the wire against 96 buried radials:
The biggest deal here is that the bandwidth is about twice that of the MA160V and its right in the 160M CW band.
NOW – the BIG TEST. How does this play on RX and TX as compared to the MA160V? Because if it plays as well or better, then there would be one strike against the MA160V and one for this antenna. Here are some measurements – where I fed the Southern leg:
- 740 – KCBS – (North Bay) – NW from Orinda – 1 S point better on MA160V
- 810 – KGO – (South Bay) – SW from Orinda – 1 – 2 S points better on MA160V
- 860 – KTRB – (South Bay) – SW from Orinda – 1 S point better on wire vertical
- 910 – KKSF – (Bay Bridge) – W from Orinda – 1 – 2 S points better on the wire vertical
- 1510 – KSFN – (Oakland) – W from Orinda – 2 units better on wire vertical
Generally speaking – it seems like the wire vertical did better higher in the AM BCB than the MA160V. The proof will be what happens at night – with some real DX signals. Daytime signals are all ground wave, so the only thing I have really proved so far is that the wire might be as good as the MA160V. The MA160V has top loading that is actually quite amazingly good – not very efficient, but an antenna that will let you get to DXCC on Top Band. The wire vertical is much taller and does have the N6BT DXU-32 as a very large capacity hat. There is no indication that there is any parasitic directionality (where the South would be the favored direction).
Listening to a nightly round table of guys up in Oregon, the MA160V and Wire Vertical are equal. This is great news because I do expect that once I phase two verticals – and I have 35+ F/B and much less loss than the MA60V (-2.7 dB), then we re talking.
CY9C was spotted up to just before the beginning of our grey line, but then they went QRT. They are on 3.507, and I hear them pretty well (on the 160M wire vertical), but its a bummer I couldn’t try to work them on Top Band tonight.
EXPERIMENT #1 CONCLUSION
With QSB, and with AA1K’s signal from Delaware, the wire vertical and the MA160V were the same, and at times the MA160V seemed 1 S Unit stronger, but that was actually due to noise – the wire is always 1 S unit lower in noise (6 dB). AA1K is in Delaware, so its less than 3000 miles, but still a good enough for a Caribbean test – where I still need enough to just about get me to DXCC on 160M.
I am really, really looking forward to seeing how the phased verticals works.
August 23, 2016
I just received the MTM Scientific W7IUV preamp kits. The price for each is excellent and they are very high quality kits – with a superb double sided epoxy PC board. They will fit in a Carlon electrical junction box – at an angle, but that’s fine – if I wanted to have a tuned circuit and preamp in the same box I would simply go for a 4x4x4 Carlon box instead of the 2x2x4 boxes.
Anywhoo, I went back and started playing around in EZNec just to ground myself about getting all excited about the Waller Flag. It would be an amazing antenna – sort of like a rotatable beverage, but how much better would it be over my 3 phased loops?
Since the Waller Flag is such a big antenna – and because it forces me to take down the N6BT DXU-32, I better be sure that’s what I want to do. Since I can’t A-B too many antennas – since they will all interact with each other and I simply have a tiny antenna space to start with, lets look at my options and compare:
- K6SE Optimized Delta (similar to K9AY Loop or EWE) – RDF = 7.79
- Full Wave 80M delta loop split into phased wire verticals – RDF = 8.79
- Three phased loops – RDF = 9.48
- Waller Flag = 11.12 at the height that I can put it up
This means the RDF improvement going from the K6SE to the three phased loops is about 1.7 dB. The split 80M delta converted to phased linear loaded verticals almost obviates the need to bother with the K6SE Optimized Delta.
Big decision point #1 – should I test the K6SE Optimized Delta or just go right to the split 80M full wave delta converted to phased wire verts? The reason why this is important:
Phased linear loaded verts on 160M – so much better than my MA160V
I would be getting TWO antennas for the price of one – a TX and RX antenna on 160M. When space is a premium, this counts. I also get 4 directions – N, E, S, W – and since the pattern is Cardioid, this covers anything I can conceivably work on Top Band.
Going from the Three Phased Loops to the Waller is also just about 1.7 dB. This means if I put up the K6SE Optimized Delta Loop this weekend and see how much better the 3 Phased Loops are – that improvement is relative to what a Waller Flag would be. If the difference seems so much better – then its worth trying the Waller. If its not that noticeable, then its not worth sacrificing the N6BT DXU-32 – not even “just for a fun experiment”.
Big decision point #2 – should I even bother with the Waller? My goal is to get to DXCC on 160M, and I can easily do that now. But I also like pushing limits technically and given my lot size. I like doing the “rediculous”, or what “The Critic” calls “The Impossible”. In fact, waxing philosophically, this is the essence of what gets me excited about ham radio. Sure – VK0EK was “The Impossible”, but now that I’ve done that, I have no need to do another – I learned and know as much about that sort of thing as I want to. There is always a point where there is a point of no return(s). Is that the Waller in my case?
Right now – via deductive thinking, my gut tells me to test the split 80M phased verticals. EZNec says it will greatly improve my 160M TX and RX and do the same on 80M. The mod I have to do is so simple – its next to zero work.
OK – that’s it – first test will be splitting the 80M Full Wave Delta into phased linear loaded wire verts. My next step will be based on the results of that test. If it goes as well as EZNec says – I would end up with my three phased loops for RX and the split delta verts for both RX and TX. That would be really cool since I can be really lazy. Hey – maybe EZNec will save me a lot of time and effort? We shall see!
My “Hypothesis” – the split delta verts will crush the MA160V rendering it useless but on RX the split delta verts will be noisier than the 3 phased loops. I predict that I will end up with:
- Keeping the N6BT DXU-32
- Split delta verts for 160 and 80M
- Three phased loops
And the MA160V will come down. I will end up with one less antenna and still have a killer station on 160 – 20M, so its a very attractive solution. But – lets see what a real scientific test with data points looks like.
August 23, 2016
I just realized, I can take the N6BT DXU-32 down and put the elements aside, and use the boom for a Waller Flag. I would purchase 8 Cabellas Crappie Poles and run the wire around those. Then, if I ever did want to put the DXU-32 back up – or even some variation of the elements (make a 5 element 20M yagi, just put up 2 elements on 40M, etc, etc) I can.
Before I go the Waller route, I have these experiments:
- Put up delta version of the K6SE flag and compare against my three loop system
- Break the 80M full wave delta and phase two elements on 160M
- Do something better than the MA160V on TX
The best thing right now is that time is on my side. I have nothing to get all worked up about until 3Y0Z, and so that’s 2 winters of Top Band fun until they go. And heck, I could even easily throw together a 20M Moxon and put it on my new Spyderbeam Aluminum telescopic mast – and raise that above the deck or side of the house just long enough for 3Y0Z and FT/G . . .
Think outside the box – good stuff!