The small SWL beam (1...30 MHz)

Use this forum to discuss any radio-related topic outside of asking for advice (check out our Questions and Advice forum for those topics). As with all of our forums, treat others with kindness and respect.
User avatar
Andrew (grayhat)
Posts: 210
Joined: Sat May 28, 2022 5:56 am
Location: JN63pn

Re: The small SWL beam (1...30 MHz)

Post by Andrew (grayhat) »

4nradio wrote: Thu Aug 25, 2022 6:18 pm Thanks for the reminder of back-to-back Bias-T boxes! I had forgotten that I can use them this way. I have an extra identical one to the Bias-T that's powering my ALA1530LN right now (not the Wellbrook supplied unit, but a ham-made pair of Bias-T's). These work well from MW on up.

What do you think of the idea of a circular SULA, with a circumference identical the square version you've modeled, and that 13dka has built? I have some construction ideas for a circular loop of plastic tubing, with the wiring & term. resistors inside, and the feed point transformer also in its proper location.
been there :D already modeled it as a circular loop, if you want I can post the NEC model, it will offer a slight more gain, but other than that, no advantage over the "diamond" version, again, for a first build, I'd start "by the book" also since the cross support can be built to be easily foldable, so allowing to carry the SULA around :)

to be clear, some parts of the SULA evolution are public. others were carried on using private messages or email, and while we (me and 13dka) may have missed something, we experimented a lot before finding the current SULA setup ;)

oh and about the SULA....

https://en.m.wikipedia.org/wiki/Booby

:D
User avatar
Andrew (grayhat)
Posts: 210
Joined: Sat May 28, 2022 5:56 am
Location: JN63pn

Re: The small SWL beam (1...30 MHz)

Post by Andrew (grayhat) »

Ok, had some time in my hands and re-ran the circular loop model in NEC, then started fiddling with parameters to try optimizing the loop, the final result is that to obtain an improvement over the diamond shaped SULA the circular one should have a radius of 78cm (about 30 inches), otherwise the loop pattern won't have a good backside "null"; with such a setup the circular loop shows a gain of -32dBi on 7MHz with an horizontal beam width of 160°, the gain at 1.8Mhz is -53dBi and the beam width 150°, going further down, at 0.8MHz the gain is -67dBi with a width of 140° - moving up to 30MHz the gain goes to -8.3dBi but the beam width widens to 200° so basically the circular loop shows better gain at the cost of a wider beam width with respect to the diamond shaped SULA.

I also tried the circular loop with a radius of 48cm to have the same circumference as the perimeter of the diamond SULA and with a radius of 54cm, that is equal to half the diagonal of the SULA, but the issue remained the same, that is a bit better gain than the diamond due to the larger area enclosed, but a less effective pattern and less pronounced backside null, so my conclusions remain the same, the diamond shaped loop is an overall better performer and offers easier portability

Then, if you want to experiment a bit yourself, below you can find the NEC model for the circular version, you can compare it with the SULA model which has already been posted here

Code: Select all

CM --------------------------------------------------------
CM File: sula_circ.nec
CM --------------------------------------------------------
CE

' symbols
SY frq=7.100                          ' test frequency
SY rad=0.78                           ' loop radius 0.48 0.54
SY hgh=3                              ' height from ground
SY ray=0.00250                        ' wire radius
SY res=530                            ' resistor
SY seg=3                              ' segmentation
SY cxr=0.00250                        ' coax radius
SY spc=(cxr*3)                        ' spacing for coax simulation
SY drp=hgh-(rad*2)                    ' drop for coax
SY bot=(spc*2)                        ' bottom of coax

' circular loop geometry
GW   1 seg 0 rad*sin(0)   hgh+rad*cos(0)   0 rad*sin(10)  hgh+rad*cos(10)  ray
GW   2 seg 0 rad*sin(10)  hgh+rad*cos(10)  0 rad*sin(20)  hgh+rad*cos(20)  ray
GW   3 seg 0 rad*sin(20)  hgh+rad*cos(20)  0 rad*sin(30)  hgh+rad*cos(30)  ray
GW   4 seg 0 rad*sin(30)  hgh+rad*cos(30)  0 rad*sin(40)  hgh+rad*cos(40)  ray
GW   5 seg 0 rad*sin(40)  hgh+rad*cos(40)  0 rad*sin(50)  hgh+rad*cos(50)  ray
GW   6 seg 0 rad*sin(50)  hgh+rad*cos(50)  0 rad*sin(60)  hgh+rad*cos(60)  ray
GW   7 seg 0 rad*sin(60)  hgh+rad*cos(60)  0 rad*sin(70)  hgh+rad*cos(70)  ray
GW   8 seg 0 rad*sin(70)  hgh+rad*cos(70)  0 rad*sin(80)  hgh+rad*cos(80)  ray
GW   9 seg 0 rad*sin(80)  hgh+rad*cos(80)  0 rad*sin(90)  hgh+rad*cos(90)  ray
GW  10 seg 0 rad*sin(90)  hgh+rad*cos(90)  0 rad*sin(100) hgh+rad*cos(100) ray
GW  11 seg 0 rad*sin(100) hgh+rad*cos(100) 0 rad*sin(110) hgh+rad*cos(110) ray
GW  12 seg 0 rad*sin(110) hgh+rad*cos(110) 0 rad*sin(120) hgh+rad*cos(120) ray
GW  13 seg 0 rad*sin(120) hgh+rad*cos(120) 0 rad*sin(130) hgh+rad*cos(130) ray
GW  14 seg 0 rad*sin(130) hgh+rad*cos(130) 0 rad*sin(140) hgh+rad*cos(140) ray
GW  15 seg 0 rad*sin(140) hgh+rad*cos(140) 0 rad*sin(150) hgh+rad*cos(150) ray
GW  16 seg 0 rad*sin(150) hgh+rad*cos(150) 0 rad*sin(160) hgh+rad*cos(160) ray
GW  17 seg 0 rad*sin(160) hgh+rad*cos(160) 0 rad*sin(170) hgh+rad*cos(170) ray
GW  18 seg 0 rad*sin(170) hgh+rad*cos(170) 0 rad*sin(180) hgh+rad*cos(180) ray
GW  19 seg 0 rad*sin(180) hgh+rad*cos(180) 0 rad*sin(190) hgh+rad*cos(190) ray
GW  20 seg 0 rad*sin(190) hgh+rad*cos(190) 0 rad*sin(200) hgh+rad*cos(200) ray
GW  21 seg 0 rad*sin(200) hgh+rad*cos(200) 0 rad*sin(210) hgh+rad*cos(210) ray
GW  22 seg 0 rad*sin(210) hgh+rad*cos(210) 0 rad*sin(220) hgh+rad*cos(220) ray
GW  23 seg 0 rad*sin(220) hgh+rad*cos(220) 0 rad*sin(230) hgh+rad*cos(230) ray
GW  24 seg 0 rad*sin(230) hgh+rad*cos(230) 0 rad*sin(240) hgh+rad*cos(240) ray
GW  25 seg 0 rad*sin(240) hgh+rad*cos(240) 0 rad*sin(250) hgh+rad*cos(250) ray
GW  26 seg 0 rad*sin(250) hgh+rad*cos(250) 0 rad*sin(260) hgh+rad*cos(260) ray
GW  27 seg 0 rad*sin(260) hgh+rad*cos(260) 0 rad*sin(270) hgh+rad*cos(270) ray
GW  28 seg 0 rad*sin(270) hgh+rad*cos(270) 0 rad*sin(280) hgh+rad*cos(280) ray
GW  29 seg 0 rad*sin(280) hgh+rad*cos(280) 0 rad*sin(290) hgh+rad*cos(290) ray
GW  30 seg 0 rad*sin(290) hgh+rad*cos(290) 0 rad*sin(300) hgh+rad*cos(300) ray
GW  31 seg 0 rad*sin(300) hgh+rad*cos(300) 0 rad*sin(310) hgh+rad*cos(310) ray
GW  32 seg 0 rad*sin(310) hgh+rad*cos(310) 0 rad*sin(320) hgh+rad*cos(320) ray
GW  33 seg 0 rad*sin(320) hgh+rad*cos(320) 0 rad*sin(330) hgh+rad*cos(330) ray
GW  34 seg 0 rad*sin(330) hgh+rad*cos(330) 0 rad*sin(340) hgh+rad*cos(340) ray
GW  35 seg 0 rad*sin(340) hgh+rad*cos(340) 0 rad*sin(350) hgh+rad*cos(350) ray
GW  36 seg 0 rad*sin(350) hgh+rad*cos(350) 0 rad*sin(360) hgh+rad*cos(360) ray

' feedline simulation
GW  50 seg spc rad*sin(90)  hgh+rad*cos(90) spc rad*sin(90)  drp  cxr
GW  51 seg spc rad*sin(90)  drp               0           0  drp  cxr
GW  52 seg   0 0            drp               0           0  bot  cxr


' end of geometry
GE  1

' ground parameters
GN  2  0  0  0  13  0.005

' wire loading and resistor
LD  7  0  0  0  2.1  ray        ' insulation
LD  5  0  0  0  58000000        ' copper
LD  0 28  1  1  res  0 0        ' resistor

' enable extended kernel
EK 

' feedpoint
EX 0 10  1  0  1.0 0.0

' frequency
FR 0 1 0 0 frq 1

' end of model
EN
HTH
13dka
Posts: 98
Joined: Sat May 28, 2022 4:27 am
Location: On or near a dike

Re: The small SWL beam (1...30 MHz)

Post by 13dka »

I got the replacement SV1AFN preamp today (the first one lacked an inductor :)) and gave it a brief indoor function test with the YouLoop.

1_YL-SV1AFN_20220912_224618.jpg
1_YL-SV1AFN_20220912_224618.jpg (29.18 KiB) Viewed 442 times

First off, as expected it does not work with 5V so I'd have to rethink my preamp power supply for portable operation. With 12V it seems to have the nominal 20dB of gain but with what looks like a noticeable gradual gain increase with frequency and what looks like no gain at all on LW/MW:


YouLoop passive on MW:
2_Passive_20220912_222201.jpg
2_Passive_20220912_222201.jpg (42.48 KiB) Viewed 442 times


With the SV1AFN preamp I get little more than "unity gain" on MW:
3_SV1AFN_20220912_222346.jpg
3_SV1AFN_20220912_222346.jpg (55.29 KiB) Viewed 442 times


This is the LANA HF (5V) on MW:
4_LANA-HF_20220912_222606.jpg
4_LANA-HF_20220912_222606.jpg (53.11 KiB) Viewed 442 times


A lot more gain down there. Since I had 12V available on the desk I decided to check for the first time what the LANA HF does with 12V. The short LANA HF manual states that it's supposed to work with 12V, even though "extended" operation with 12V is not recommended. I didn't intend to use it with 12V but I honestly expected it to survive more than 10 seconds, which it didn't. I attached the power supply to the Bonito CPI1000 bias-T unit, the LANA came on but with very little gain, I disconnected the power, checked the connections and plugged the 12V back in, it came on again and then the LED on the LANA went out. :(

I double-checked the power supply output:

5_12V_20220912_223111.jpg
5_12V_20220912_223111.jpg (33.57 KiB) Viewed 442 times

Yet the LANA HF was dead, the third one altogether (NooElec was very helpful and replaced the first 2, of which 1 died while testing it on the SULA, the other one lost a few dB of gain elsewhere since I bought it).

Moving on, here's the SV1AFN preamp on LW:

6_SV1AFN_LW_20220912_224104.jpg
6_SV1AFN_LW_20220912_224104.jpg (51.23 KiB) Viewed 442 times

The remaining LANA HF:

7_LANA-HF_LW_20220912_223833.jpg
7_LANA-HF_LW_20220912_223833.jpg (51.4 KiB) Viewed 442 times
Of course I have yet to test the SV1AFN properly at the dike, particularly because the "visual" gain does not say much about the actual reception but it could turn out to be of somewhat limited use for the SULA this way. It also gets pretty warm and I'm afraid that means it will drain the battery a lot faster than the LANA HF. The LANA HF might be a bit sensitive (the other one died after A/B switching SULA and reference antenna a few times) and I guess I have to bite the bullet and order the W7IUV 2N5109 preamp or the 2SC5551 equipped model too, which burns up battery for the relays we don't really need for RX-only operation. The 2SC5551 model seems to have a particularly low noise figure which is certainly interesting.
User avatar
Andrew (grayhat)
Posts: 210
Joined: Sat May 28, 2022 5:56 am
Location: JN63pn

Re: The small SWL beam (1...30 MHz)

Post by Andrew (grayhat) »

13dka wrote: Mon Sep 12, 2022 9:52 pm I got the replacement SV1AFN preamp today (the first one lacked an inductor :)) and gave it a brief indoor function test with the YouLoop.

First off, as expected it does not work with 5V so I'd have to rethink my preamp power supply for portable operation. With 12V it seems to have the nominal 20dB of gain but with what looks like a noticeable gradual gain increase with frequency and what looks like no gain at all on
This is strange, see, the GALI-84+ declares an operating range (and gain) from DC to 6 GHz, and the SV1AFN web site says that that preamp works from LF up to 4GHz; did you try mailing SV1AFN and asking some clarification ? as for the 12V, the GALI datasheet states that the IC operating voltage is around 6V, but if you then look at the SV1AFN schematic
.
29-11-2019-16-25-5de1468186347.jpg
29-11-2019-16-25-5de1468186347.jpg (83.78 KiB) Viewed 429 times
.
we can clearly see that the preamp wants 12V, this is probably due to R1/R2 which are dropping the voltage (the power comes from the Bias-T formed by C2/L2); also, looking at the circuit, the frequency range limit is most probably set by C1/C2 and L1/L2, but then given that SV1AFN states that the unit works from LF, the fact that it has very little gain down on MW seems strange
A lot more gain down there. Since I had 12V available on the desk I decided to check for the first time what the LANA HF does with 12V. The short LANA HF manual states that it's supposed to work with 12V, even though "extended" operation with 12V is not recommended. I didn't intend to use it with 12V but I honestly expected it to survive more than 10 seconds, which it didn't. I attached the power supply to the Bonito CPI1000 bias-T unit, the LANA came on but with very little gain, I disconnected the power, checked the connections and plugged the 12V back in, it came on again and then the LED on the LANA went out. :(
Never tried the LANA-HF with 12V, the NooElec infos on site say that the preamp may survive for a very short time to a 12V supply, but they warn that it may be quickly damaged, and ... well, you demonstrated it :( ! My wild guess is that while the IC used may accept 12V, the passive components (resistors/capacitors) surrounding it aren't rated for that voltage <sigh>
Of course I have yet to test the SV1AFN properly at the dike, particularly because the "visual" gain does not say much about the actual reception but it could turn out to be of somewhat limited use for the SULA this way. It also gets pretty warm and I'm afraid that means it will drain the battery a lot faster than the LANA HF. The LANA HF might be a bit sensitive (the other one died after A/B switching SULA and reference antenna a few times) and I guess I have to bite the bullet and order the W7IUV 2N5109 preamp or the 2SC5551 equipped model too, which burns up battery for the relays we don't really need for RX-only operation. The 2SC5551 model seems to have a particularly low noise figure which is certainly interesting.
if the gain is so low down at MW, I've little hope the SV1AFN will be so useful for the SULA, on the other hand, I believe that asking SV1AFN some clarification about the low gain may be due

At this point, it remains to see which preamp may be suitable for the SULA, the LANA-HF isn't bad since it demonstrated to work and since it's widely available, but having more choices would be nice, I was looking at some preamps which look interesting, but they aren't commercial ones, and even if some of them may be available through various sources, they aren't easily found as the NooElec <sigh>
13dka
Posts: 98
Joined: Sat May 28, 2022 4:27 am
Location: On or near a dike

Re: The small SWL beam (1...30 MHz)

Post by 13dka »

Andrew (grayhat) wrote: Tue Sep 13, 2022 7:48 am Never tried the LANA-HF with 12V, the NooElec infos on site say that the preamp may survive for a very short time to a 12V supply, but they warn that it may be quickly damaged, and ... well, you demonstrated it :(
Nooelec wrote: Though there is protection circuitry on LaNA HF Barebones for overvoltage conditions--and voltages of up to 12V DC should still work and will not damage the device--it is not recommended for long-term usage. Kindly note that damage resulting from overvoltage conditions would not be covered under the standard warranty.
I wouldn't have tried that otherwise. BTW the image shows the Bias-T input voltage, the voltage on the ANT jack is 0.2-0.3V lower. I hope to get the SV1AFN preamp tested with the SULA at the dike tonight, Maybe that's just some interaction with peculiarities of the YouLoop I'm seeing there.
User avatar
Andrew (grayhat)
Posts: 210
Joined: Sat May 28, 2022 5:56 am
Location: JN63pn

Re: The small SWL beam (1...30 MHz)

Post by Andrew (grayhat) »

13dka wrote: Tue Sep 13, 2022 11:41 am I hope to get the SV1AFN preamp tested with the SULA at the dike tonight, Maybe that's just some interaction with peculiarities of the YouLoop I'm seeing there.
Uhmmm... I missed that <sigh> ... ok, the NCPL (YouLoop) impedance is FAR AWAY 50 Ohm, the 1:1 BalUn there is only used to keep the loop balance (to some extent, there's a mod improving that, but that's a different topic) so the SV1AFN is seeing a (probably large) input impedance mismatch and that may explain why it isn't playing well, if that's the case, then the preamp should work better with the SULA, since the latter has good impedance match over the whole operating range
13dka
Posts: 98
Joined: Sat May 28, 2022 4:27 am
Location: On or near a dike

Re: The small SWL beam (1...30 MHz)

Post by 13dka »

Andrew (grayhat) wrote: Tue Sep 13, 2022 12:43 pm
Uhmmm... I missed that <sigh> ... ok, the NCPL (YouLoop) impedance is FAR AWAY 50 Ohm, the 1:1 BalUn there is only used to keep the loop balance (to some extent, there's a mod improving that, but that's a different topic) so the SV1AFN is seeing a (probably large) input impedance mismatch and that may explain why it isn't playing well, if that's the case, then the preamp should work better with the SULA, since the latter has good impedance match over the whole operating range
I wish you were right.:/ I tried the preamp at the dike with the SULA tonight and it looked like it has indeed (more or less) a similar gain curve as the SULA, weak on MW and better with increasing frequency. The result was basically no reception on LW, very little on MW, still pretty bad on 20m and the "break-even point" (where the gain was comparable to the LANA HF) was on 10m. So it looks like something isn't right with that preamp but I'm going to check the coax and connectors tomorrow to make sure there isn't something off on that side, how much voltage is left on the other end of 15m coax etc.. before I contact Makis again (I really hate being a high maintenance customer!).

After I swapped the preamps and batteries everything was back to normal though and I enjoyed the general function of the antenna with some pretty healthy signals from the US. Everything from the east was pretty weak though and when I tried to peak the very weak signal of AUS VOLMET on 11387 kHz I had this situation again where thunderstorms over France and Spain were for the most part ending up in the backside minimum. Turning the antenna a little to the side didn't reduce the signal from Australia but lots of crashes started triggering the AGC and made it hard to hear the station until I turned it back. This really is a fun antenna. :)

SULA_w_SV1AFN_LNA.jpg
SULA_w_SV1AFN_LNA.jpg (58.17 KiB) Viewed 406 times
(I usually take a pic of the antenna when I set up the station at the dike so I know later what recordings were made with what antenna, tonight I got this dramatic picture.)
User avatar
Andrew (grayhat)
Posts: 210
Joined: Sat May 28, 2022 5:56 am
Location: JN63pn

Re: The small SWL beam (1...30 MHz)

Post by Andrew (grayhat) »

13dka wrote: Wed Sep 14, 2022 12:09 am I wish you were right.:/ I tried the preamp at the dike with the SULA tonight and it looked like it has indeed (more or less) a similar gain curve as the SULA, weak on MW and better with increasing frequency. The result was basically no reception on LW, very little on MW, still pretty bad on 20m and the "break-even point" (where the gain was comparable to the LANA HF) was on 10m. So it looks like something isn't right with that preamp but I'm going to check the coax and connectors tomorrow to make sure there isn't something off on that side, how much voltage is left on the other end of 15m coax etc.. before I contact Makis again (I really hate being a high maintenance customer!).
SIGH !! I doubt the issue may be due to voltage, although the fact that the preamp doesn't perform even going up to 20m isn't normal imHo, add to this that the preamp is sold as "LF to GHz" and, sincerely, there's something not "matching" here, I understand your point, but I believe that asking Makis for help/infos may be the right thing to do
After I swapped the preamps and batteries everything was back to normal though and I enjoyed the general function of the antenna with some pretty healthy signals from the US. Everything from the east was pretty weak though and when I tried to peak the very weak signal of AUS VOLMET on 11387 kHz I had this situation again where thunderstorms over France and Spain were for the most part ending up in the backside minimum. Turning the antenna a little to the side didn't reduce the signal from Australia but lots of crashes started triggering the AGC and made it hard to hear the station until I turned it back. This really is a fun antenna. :)
Well, at least that demonstrated that the SULA needs a decent preamp, as for crashes from thunderstorms, the only antenna I'm aware of, which is capable of attenuating them is the LoG, yet the backside "null" of the SULA seems to have some effect on those :D
(I usually take a pic of the antenna when I set up the station at the dike so I know later what recordings were made with what antenna, tonight I got this dramatic picture.)
Hey, a "cross" against dark stormy clouds is something :D !
Post Reply