Steerable SDR receiving antenna???

[W1DAN]

Hi Folks:

Just wondering....

I have read about the 4-square antenna, and am wondering if anyone has sent 2 or 4 receiving verticals (I am thinking coil-loaded 5-10 foot vertical sections) to individual SDR receivers and a common computer app?

With DSP phasing and filtering, is there any advantage to doing this steering digitally versus at analog RF frequencies?

I have a friend in Mississippi who is a 160m DX hound, and he has high QRN noise. Just wondering if he could null out noise from multiple specific directions or get a tight beam-width in the direction he may be interested in. Also wondering if there is any advantage to coorelation-based noise reduction from multiple SDR receivers.

Thoughts?

Just wondering.... :-)

Dan

[WA1GFZ]

Dan,
I'm running dual HPSDR receivers with beam steering. It is cool. I use it with a pair of 40 meter delta loops on 40. I also bought 4 cliften labs front end kits to build a 4 square with e probes. I plan to put up a 4 square array. You can select 4 directions with delay lines. Check out ARRL low band dX ing, DX engineering, or Hi-Z. The system phase line switching is pretty easy. It takes 3 DPDT relays and 3 delay lines.
I also have 2 loaded delta loops 15 feet high and 30 foot base. Load is 1K and a 4:1 BB transformer in the other corner. I have 1 facing west and the other east. Good directivity. I also had two of them phased to the west that also worked well. Check out the Dallas files for RX ants.
E probe does not need matching look at clifton labs. Jack posts his schematics.  He sold me board kits with the parts for a good price.

[KM1H]

Have him look into a Circle 8 array, its 8 20' verticals in a 200-300' diameter circle. Reportedly the rear null can be in the -40dB area.

[Steve - K4HX]

The Circle 8 doesn't have anything approaching that sort of F/B, not that geometric F/B is a good measure for receiving antennas anyway. A Circle 8 only uses 4 elements at a time, two end-fire groups in a broadside. No magic.

There is a ham that has done the multi-channel beam steering with independent SDRs and his own controlling SW several 5 or more years ago. Look up K1LT. The Rocky sw had the capability for two channels several years ago but appears to have discontinued it. PowerSDR will also do two channels. Check out the demos on the Flex site or YouTube.

The advantage to doing the steering digitally are more flexibility (you can easily adjust the null right where it is needed at any given freq or time). The draw back is the sw complexity and possibly latency.

[WA1GFZ]

Deep nulls are not stable over time. 20 dB is usually a better long term number. I have not noticed any latency issues since we converted to 100T ethernet from USB. It will be nice to set it to 1GHZ someday. Usually I flip between loaded loops and 40 meter delta loops.  K5SO has been doing the software for HPSDR

[Steve - K4HX]

How did you measure the latency?

[w3jn]

500 smackers gets you a dual-channel SDR receiver with a 100baseT ethernet interface, 480KHz bandwidth

Not sure of the dynamic range, etc., but it does have AGC for the front end.

http://uvb-76.net/p/sdr-mk15-andrus.html

[flintstone mop]

I have had reasonable success nulling out noise with my magnetic loop antenna and a antenna rotor.
On a beverage, I think you can adjust the terminating resistor value and achieve the same??? dunno........

[WA1GFZ]

Steve,
Many times I will run the racal ra6830 at the same time the HPSDR is on.
Ever since the Metis ethernet board came out the Latency went down. I figure it is around 50ms just listening. I never measured it. That is with 2 receiver modules running. It was a lot worse with USB.

[Steve - K4HX]

Yep, that's the real test, concurrent analog and digital systems.

The biggest complaints on latency come from the QSK CW guys.

[ke7trp]

For months, I have been looking for a small RX antenna that had some good FB ratio.  The Small loops are nice but they rx off the ends so if you point it west, You hear east just as loud.

[KM1H]

The Circle 8 doesn't have anything approaching that sort of F/B, not that geometric F/B is a good measure for receiving antennas anyway. A Circle 8 only uses 4 elements at a time, two end-fire groups in a broadside. No magic.

Many have reported 30-40dB on groundwave which is where it really counts to minimize the local crud.
No realworld antenna has stable F/B on skywave.
As with any phased array it is very important to match all the individual feedlines as well as have plenty of ferrite on them

[Steve - K4HX]

People have reported being abducted by aliens too.

You can get 40 dB on groundwave with a small loop. A Circle 8 is overkill just for nulling local interference. The value of that system is a very good RDF that can be pointed in 8 directions - a great receiving antenna for DX. It's not small either.

Clark, take a look at combining the outputs of a loop and a whip. Now you have a null in just one direction.

[KM1H]

And a loop doesnt do squat for rejection on skywave, thats why the aliens found you.

The circle 8 is a nice alternative for those without a lot of acreage, just a 200' circle and no radials.

[Steve - K4HX]

You're the one who brought up groundwave nulls. Which is it, skywave or groundwave? Make up your mind.

The Circle 8 needs a circle diameter of 377 feet for 160 meters and half that for 80.

No matter, it's overkill for noise rejection and not the best system for good nulls. It wasn't designed for nulling. It was designed for a narrow forward lobe, about 50 degrees. It has no ability to steer the elevation angle of the null.

There was a good article by G3LNP in QST, Oct 2010 on a loop system that produces steerable skywave nulls. It's no larger than a K9AY.

[KM1H]

Its for whatever the OP's friend needs, the C8 will do it all well and only 200' is needed for 160 as the design keeps getting refined. The narrow beamwidth is far more important than null steering and if built to close tolerances the F/R follows.
The RDF says they work much better than garden size loops, triangles, etc. which are one option for the land challenged.

But of course Ive never heard you in 160M CW pileups either. 

[Ralph W3GL]

Aw, you guys with all this computerized and quasi new technology,  I'll still take
the FLR-9 Woolyweaver for the best in steerable receiving antennas, pricy yes, but
most effective...

[KM1H]

What the heck is a few acres overlooking the ocean got to do with it....its only money that we paid.

[WD8BIL]

.......the C8 will do it all well and only 200' is needed for 160 as the design keeps getting refined.

That leaves me out. My lot is only 150" wide!

Think I'll K9AY it!

[W1DAN]

Hi Folks:

Thanks for the responses. My friend Charlie WD5BJT is cash-inhibited, so I am trying to talk him into homebrewing something that is not too elaborate or expensive. So I am thinking of 2 or 4 antennas either combined and phased in the analog RF domain or in DSP. The Circle-8 antenna is not what we want to do initially. Charlie wants to null local QRN and obtain some directionality for night-time DX on 160m.

Talking about this is more for our learning, not sure what we'll do. Do not know if phase-locked Soft-Rock SDR receivers and a single DSP application will being signals in far better than analog.

Thanks,
Dan

[KM1H]

My friend Charlie WD5BJT is cash-inhibited

Try a pair of staggered phased Slinkys. About 5 stretched over 150-175', 15' seperation and staggered 90'.

I get a solid 20-25dB local F/B with a 500' BOG as well as 2 wire reversible regular Beverages. The BOGS are fed about 50' from neighbors with all sort of noisy crap. Havent missed any new ones on 160/80 yet due to noise since I rebuilt it all starting 2 years ago. Notch filter, and VBT do the rest.

[W1DAN]

Carl:

Charlie's money situation is real. I will PM you to explain.

Thanks,
Dan

[KM1H]

Im sorry about that Dan and I deleted those comments. From your post it sounded humorous.   and the ass in assume got me in the ass.

Carl

[W1DAN]

Carl:

Thanks. No harm done!

Frank:

Do you feel that your dual SDR's and software provide better results than just analog phasing?

Charlie and I have read the Clifton Labs and DX-Engineering web sites. May do the Clifton Labs boards.

Thanks,
Dan

[WA1GFZ]

Dan I have the option of variable phase unlike analog with a single phase delay.
A lot more bucks though.