BSB Squarial - anyone got one lurking?

[radiogareth]

Just out of interest, does anyone have an old BSB 'Squarial' lurking in their 'one day' box/Shed/House etc?
No rush, but if you do and would part with it, let me know please, either on here or via the PMs.
Thanks
Gareth

[M1EGI]

Hi Gareth,

By Squarial, do you mean the very small dish? or the flat panel version?

To me, squarial is the flat panel unit... if this is what your require, then I have a small pile of them!

Let me know if this is what you are looking for?
Also, either way, what are you planning on doing with it? (just being nosey)


73 Gary M1EGI

[radiogareth]

Hi Gary, Yes, its the Flat square one I was looking for, I have a couple of the small dishes doing good service on something else.
No rush, I'll be at the RSGB convention next weekend if that helps, or we can sort out something else if not.
Thanks
Gareth

[M1EGI]

Hi Gareth,

Unfortunately, I won't be at the convention...

What do you plan on doing with it?
Do you require one with the LNB fitted or not?

You can modify these to accept WG17, and I have used one to RX QO-100 NB transponder.
Just keep in mind, they are circular polarised, but I understand they can be modified to linear polarisation.

We shall have to arrange shipping...

73 Gary M1EGI

[radiogareth]

Hi Gary, I'd be adapting it to WG initially, its just one of those interesting re-purposing things I'd like to try.
I don't think the LNB will have any use, from memory they were a bit high, although I do recall digging the glue out of one of the small dish LNBs and tweaking the DRO screw to get it down a bit. Old tech though now....
Thanks
Gareth

[g4hiz]

Hi Gary and all,

the Squarial is an interesting antenna, having experimented with it for the reception of terrestrial as well as QO-100 NB signals. I did attempt QO-100 WB reception, but it seemed a few dBs short of performance for success with my setup. Being a passive antenna, I intend to explore terrestrial Tx possibilities also.

I presented my modified unit (with a new LNB fitted) at the Crawley Microwave Round Table last month and if interested have a follow-up article in the forthcoming Scatterpoint magazine of the UK Microwave Group - recommended to join if not already a member!

Attached is a photo showing my LNB adaptation.

73
Jen

[M1EGI]

Hi Jen,

I shall look forward to your Scatterpoint article!
I modified mine in a similar fashion to your photo, but I took mine apart to drill and tap two more mounting holes for the waveguide transition.

Unmodified these are circular polarisation, I remember reading a webpage about converting these to linear, but I'm not sure how confident I am in the method. (antenna test range required) BUT this could gain you 3dB, so maybe worth a try?
http://g3rfl.co.uk/bsb.htm

Anyone interested in playing with these, check out eBay at the moment as several are listed (including brand new)

73
Gary M1EGI

[g4hiz]

Hi Gary,

Indeed, the Squarial was intended to receive the UK WARC-77 DBS channels at roughly 11.7 to 12.2GHz, with RHCP. However, at 10.5GHz and with the test setup used, the antenna discriminated by about 16dB between horizontal and vertical polarisation, indicating that it was most likely no longer circularly polarised at the frequency used (being somewhat elliptical probably). If it had been circular, antenna rotation should have not made a difference in received signal level.

In terms of gain, there are a number of ways to estimate this, but the bottom line was how well did it do compared with a reference antenna with a similar LNB? Indications were that the antenna gain looked pretty reasonable, if not quite good, probably down to the efficiency being better than a dish size-for-size.

I intend to put some RF into a Squarial to look at possible transmit capability, with a plan to check the return loss initially and after ramping up power. I have 20W or so at my disposal so will see how it goes!

Depending on RL, a circulator may be recommended for transmitter protection.

73
Jen

[M1EGI]

Hi Jen,

Just finished reading your Scatterpoint article, very interesting!

Apart from my hardware mods to fully support WG17, and a quick RX test on QO-100 NB, I didn't get around to further tests...
As you state, your tests at 10.4GHz indicate that the polarisation is no longer circular.

Please keep us posted with the TX result, I think I would run with an isolator regardless of power (especially with a 20watt PA) hopefully as you ramp up the RF, nothing will melt, or worse!

73 Gary M1EGI

[g4hiz]

Hi all,

I can see that there has been a bit of interest in this topic and as such I wish to share a preliminary measurement made of Return Loss vs. Frequency for one of the Squarials that I have. These measurements were made at low power (0dBm) and do not necessarily show what would happen if higher power was to be applied, as a some point, internal electrical failure will occur.

I do not currently have access to a Network Analyser, hence the plots were derived from reflected power measured using a directional coupler and should be taken as INDICATIVE ONLY - hence the usual caveats apply and always check yourself before attaching any expensive radio equipment!

73
Jen