Hi all,

I wanted to summarize some simulations made here (MMANA_GAL), and based on Internet researches as well as my own calculations/simulations.

The goal is to prepare next winter for the low bands based, improving the actual HF2V.

1st thing to know:

My SWR is 1:1 on 40m, for a 1/4 full-size vertical which impedance (Rr) = 36 Ohms theoretically.

Because of my 1:1 SWR, I logically conclude that my losses (GND plane etc) equals to 50 - 34 = 16 Ohms (= Rp)

OK, let's consider this figure.

Simulating the HF2V (the simulation file is of course available upon request !) with its original dimensions (coils set at 1m from GND), I obtain

80m : Rr = 11.5 Ohms with a loading coil = 5.96 µH

40m : Rr = 34.5 Ohms with a loading coil = 4.71 µH

The famous formula Efficiency = 100 * Rr /(Rr+Rp), I finally got with my original HF2V

80m = 42%

40m = 71%

HOW TO IMPROVE THIS ????

1st step

Let's put the coils higher on the vertical portion (which means coil value will increase --> be ready to contract or extend the coils position after this modification)

2m high

80m --> Rr = 13.6 Ohms and L = 6.22 µH => efficiency = 100*13.6/(13.6+15) = 47.5%

40m is unchanged !

3m high (still accessible from gnd for the operator, HI !)

80m --> Rr = 16 Ohms and L = 6.48 µH => efficiency = 100 *16 / (16+15) = 52%

40m is unchanged !!!

Conclusion :

Shifting the coils 2m higher improves efficiency by 10% !!!!! For an output power of 100W, 10 more watts are radiated instead of being wasted in the GND.

2nd step

Let's increase the height of the HF2V from 9.8 up to 12m high, with the coils still at 3m high.

80m --> Rr = 17.5 Ohms and coil = 6 µH => efficiency = 100 * 17.5 /(17.5+15) # 53.8%

3rd step : GND losses

Let's decrease the Rp from 15 down to 10 Ohms by 1 Ohm step (this is purely calculatory) in the very last configuration (HF2V modified, coils @ 3m high, total height = 12m => Rr = 17.5 Ohms)

Rp = 15 Ohms => efficiency = 53.8%

Rp = 14 Ohms => efficiency = 55.5 %

Rp = 13 Ohms => efficiency = 57.4 %

Rp = 12 Ohms => efficiency = 69.3 %

Rp = 11 Ohms => efficiency = 61.4 %

Rp = 10 Ohms => efficiency = 63.6 %

Another 10% efficiency are recoved by decreasing Rp from 15 down to 10%.

Conclusion:

The original HF2V is a good antenna (in 2 years time, I got > 150 DXCC and 35 zones on 80m with 500-600W PEP out)

Now, it is time to climb another step because its original efficiency on 80m is around 42% (only), and because new ones on 80m are rare...

By increasing its length by 2m and shifting the coils from 1 up to 3m high (requires a 2m aluminium mast of a good diameter, not that hard to find), already some slight adjustments of the coils would bring 10% more efficiency easily. This can be doen without changing the coils, but just by stretching them !

Optimizing one's losses (gnd plane for example), another 10% efficiency can be found.

20% more efficiency, what's the result in terms of DX'ing?

Let's consider an output power of 500W from the linear.

Originally, with 42% efficiency, only 210W were effectively radiated !!!!

With 20% more efficiency, now 310W are radiated, 50% more power are radiated, isn't it huge ??? !!!!!!!!! ????

Well, it's like you were transmitting with 600W instead of 400W, sometimes this is enough to get over the noise floor.

Same principle applies on the RX side (even if a dedicated RX antenna is always preferable for S/N improvement).

Last thing :

Well's experiment this for the next low band season !!!!!!!

73

Ronan, F8AFC

Hi all,

Long time that I didn't receive any QSL, but 4 in a row yesterday.

NP4A on 10m --> I now have KP4 confirmed on ALL bands.

Z21BB on 15m --> Zimbabwe now confirmed on the 5 "high bands" (waiting QSL for 40m too)

E4X on ALL bands --> 2 new band slots confirmed on 12/10m.

Nice ones, and once again, tnx for QSL'ing !

Ronan, F8AFC

Hi all, Not so many activities (nor propagation ?) in this summer, but always nice to hunt for some "outside of EU" DXCC even if they have been confirmed for a long time.

This time, I was interested in XT2EME which I miss on both 80/40m bands. I could get them on 40m, but no real activity on 80m (to much QRN they said). i also got them in QRP (5W), which is a new one in QRP conditions. Not that bad !

That was my #205 on 40m...Hope to get closer from the 225 soon (my next target there !)

Ronan, F8AFC

Hi all,

I received yesterday a # 200 QSL package from the French buro, thanks to all for QSL'ing !!!!!!!!!!!!!!!!!

Among those around 200 QSL, I'd like to especially thank the following stns for new band slots / zones now confirmed !

RA0QD, NEW WONE on 17; Zone 19 !!!!)

LZ2009KM on 12m (last band for LZ confirmed everywhere )

OX3KQ on 17/15m

OZ2AR on 80m (last band for OZ confirmed everywhere )

V31WA on 40m

SV7LPL on 40m

CT7LHM on 12m and 6m

CQ2I on 80m

ES2IPA on 80m

ES1BA on 12m

US5CB on 12m

RU6HJ on 80m  (last band for UA confirmed everywhere )

PA3GSU on 17m

PD0ROc on 40m

PE2KP on 10m

LY5W on 40m

EI5HV on 40m

19 new band slots, including 3 additional DXCC now confirmed on ALL bands, and including a new zone

73 !!!!!!!!!!!!!!

Ronan, F8AFC

In a week-time, I managed to work them on all bands from 80 up to 10m, incl WARC's.

OK, you will say, E4 is not that far from France, and you are right.

But despite of a short path and relatively good propagation to this area, we have in F a wall that is VERY hard to come over : the EU ZOO !!!!!

I started by a 17m QSO, just to get a friend of mine who was there (Flo, F5CWU). Then 20, then 15m. But nothing new for "my" DXCC.

Then a 40m QSO, during a rare RX activity below 7.1MHz (remember that in France, we are still NOT allowed to TX above 7.1MHz !!!!!!!!)

Then the WE time, generally good at midday time for the high band sporadic propagation. That was the toughest : Wait for the prop to peak in Western Europe and go iover the mediterranean wall.....If E4 is relatively easy for French hams, it is even easier for SV and I stns....no comments there. But there we are, 12/10m in the log too, enabling me to close this DXCC on all bands (there were my 2 needed bands !)

Now that was time for the grand Chelem, and get them on 80m. What a KW race, splatter festival, crocodiles stations. First evening they were on 80SSB, I couldn't get through.

2nd evening, I had to wait until 01:30 in my morning time to go through, and that was a lucky one !!!

What's next ? Well, let's contact this one in QRP 5W: 20m was easy at my sunset. 17m was a bit more difficult, and I was calling 30min 5KHz above the split end. That worked !

10m was extremely luck, signals peaking S9 here, 15KHz split, that was my chance. and I did it.

15m was tough in QRP, 1hour before my SS, but thanks to a wide split, I came through in about 1 hour (!)

12m, well, I ddin't really try there, except yesterday evening. But 1 hour after SS, their signal was only S2-S3 here with lots of QSB.

I was also logged on 30m CW (see their on-line log), but that was not me, I don't ahen antennas for 30m and I'm not a CW op....

I also tried on 6m band, but with my HF Hexbeam with its 45/50° elevation angle there, I've never heard them.

What's the next expedition you said ?????

73

Ronan, F8AFC