Carl Reade

2 hours ago, robin_astro said:

Could be useful when fine tuning the system/dish to  optimise it perhaps?  Integrating a continuum signal over a wide bandwidth 

Robin 

Yep nail on the head!

37 minutes ago, Coto said:

I didn't really understand what you're trying to do. What is a "total power element"? Are you trying to replace the SDR with a different type of receiver? What more kind of "capabilities" will you be able to achieve with the new type of receiver? The only thin I can think of is wave amplitude, phase and waveform detection, but I don't think that's what you're trying to achieve (no "oscilloscope"/"spectrum analyzer" mentioned).

Basically the same as what you do with a satellite meter and LNB.

My next step on the project is to add a total power element to the scope. I have an old RA project from years ago which has a simple diode detector and a DC amplifier circuit. My plan is to bypass the dongle and connect the dish/ amp chain to this and and an ADC to measure the voltage and see what results I get.

I could be way off the method. If it works it will add a bit more capability.

Carl

52 minutes ago, Coto said:

For the 1420 MHz bandpass filter, I've found this one: http://adsbfilter.blogspot.com/2015/06/hydrogen-line-1420-mhz-filter.html [20 EUR + 7 EUR shipping (total = 30.75 USD)]. I think it's a pretty good deal for its quality/price.

Now that I've taken care of the filtering, I'm curious as to which LNA would be more ideal for me: http://g8fek.com/uploads/9/4/4/3/94435411/sba13001700-box_a5.pdf or http://g8fek.com/uploads/9/4/4/3/94435411/sba12501450-sma_a5.pdf ? They seem to share similar characteristics (in terms of NF and Gain), but I'm not sure what's best if I'll be looking to pick up HI emissions only (1420 MHz) (and won't care about other frequencies unless I switch up the feed etc.). Both LNAs cost £145.00 + £9.50 Shipping (total = £154.5 = 173 EUR = 197 USD).

As for RAS, I don't think I'm getting anything from them any time soon. The $199 LNA (with NF=0.29db) might have been worth it if the shipping was not $45 (!) to Greece and their customer support was a bit more helpful.

Hi I have the 1300/1700 one. It incorporates the OH line band at 1.6Ghz. the other incorporates the amateur band at 23cm for moon bounce communication at 1.2Ghz. that's the only real difference.

9 hours ago, Coto said:

@Carl Reade I noticed that you've got a Radio Astronomy Supplies LNA in there. Is it this (https://www.radioastronomysupplies.com/store/p9/www.radioastronomysupplies.com/store/p9/1420_MHz._HIGH_PERFORMANCE_LNA.html.html) or this (https://www.radioastronomysupplies.com/store/p56/www.radioastronomysupplies.com/store/p56/1420_MHz_ULTRA_HIGH_GAIN_LNA.html.html)?

I've been thinking of getting an LNA and RAS seems to be the only supplier who sells very low NF LNAs. Their customer support is pretty terrible, so you're probably the only one who can answer this: what's the quality of the LNA? How much does it help? Does its NF really seem to be as low as advertised? $199/$225 + Shipping costs really make me think well before getting the proper LNA for Hydrogen-line observations, so your opinion can really be helpful here!

EDIT: Oops, didn't notice you had noted "Filter"... By its dimensions and shape I thought it was an LNA. The only bandpass filter they've got for 1420 MHz is this: https://www.radioastronomysupplies.com/store/p12/www.radioastronomysupplies.com/store/p12/RAS_1420_MHz_BAND_PASS_FILTER.html.html which has a different shape.. Where did you get yours?

Hi the filter I'm using is quite a few years old from RAS. It is the three rod design. I suspect that the new one is probably improved and now etched on a circuit board. Both do the same thing.

RAS have been around for a long time designing and building equipment for the RA sector I would say their noise figures are accurate. They are also filtered for the band which is a big plus.

The cheaper LNAs on eBay will work but they are mass produced and basic so their noise figures would not be accurate especially as they are not filtered and wideband. They would depend on your local RF environment.

The cheaper one I recommended a post or two above I have seen working.

Here is the link to the one I am using at the dish. These are designed, built and tested by a professional company and supply to the RA community, again I would trust their figures and you can see my results here with it.

http://g8fek.com/index.html

So the two routes are either purchase a more expensive one designed for the job or go for the cheaper type which you will need a filter for and need to screen. Both will work.

What I have learned in this project is software processing is half the job as well. You will be detecting the H line but not even realising it. The better the LNA and antenna the easier it is to discern from the noise.

Hope this helps Carl

46 minutes ago, ZijadSarajevo said:

Thy,a lot,i saw many examples of feed horns,each was equally good,it is important that alu sheet must be galvanized.I saw one guy made it from a single PVC tube and alu tape which was wrapped inside the tube.But alu coffee can,or proper alu sheet is efficient.I will stick to the right thing...

Ckecked your Bias Tee by using pic,i hope it is the same you bought...It is quite expensive,i hope there is a bit cheaper one and also efficient...I can't do anything without it at all...

https://www.ebay.co.uk/itm/Axing-TZU-15-02-Remote-Power-Inserter-max-1-A-for-Satellite-CATV-terrestrial-5/362431982015?epid=1719961720&hash=item5462a129bf:g:XF0AAOSwPXdblFAn:rk:1:pf:1&frcectupt=true

You could make one. It is just an RF choke and a capacitor. Nothing to them really.

45 minutes ago, ZijadSarajevo said:

Domestic vendors has no any of necessary parts which are needed for assembling in their stores.Therefore,i've just made my first offer via Ebay.Starting with two In Line Amplifiers.

 

 

Nice case for internal parts.Ok,which "feed" dimensions are best for 1m dish?And,you did not emphasized earlier anything about Bias tee,or i just missed to read about it! @Carl Reade

Hi the dementions of the can stay the same no matter what dish size, however I use a biquad feed there is a link to it's calculator in earlier post.

http://www.setileague.org/hardware/feedchok.htm

The bias fee was from eBay as long as it's within the frequency range any will do. This one is 0.5 - 2000Mhz.

Hi here is a diagram and pic of what I put together. There are a lot of different cable connectors at play due to components being different. Most LNAs are SMA connectors and for the coax (WF100) F type connectors. So plan what adapters you will need to put whatever components you use together. I.E SMA male to female F etc.

For example the dongle will need a male SMB to female F connector tail lead.

Carl

22 minutes ago, ZijadSarajevo said:

@Carl Reade That vendor does not ship to Bosnia and Herzegovina,but i think this one could be equally good as previous.....I mean it is same.

https://www.ebay.co.uk/p/LNA-50-4000-MHz-RF-Low-Noise-Amplifier-Signal-Receiver-Spf5189-NF-0-6db-Ark/12006537045?iid=163253465136&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20160323102634%26meid%3De686c2d8f0d34eed957b3d6418a88df1%26pid%3D100623%26rk%3D2%26rkt%3D6%26sd%3D263793459193%26itm%3D163253465136&_trksid=p2047675.c100623.m-1

But,i can also check in the local shop that also selling satelite and cable equipements.

 

Yes it's the same one should be fine. The satellite shop should have 20db line amps.

Have you thought about a feed for the dish?

26 minutes ago, ZijadSarajevo said:

@Carl Reade  Carl I would like to thx for all that suggestions....Link you gave me is a very usefull )going to add them on favs),i see that guy used can instead LNB,but is it possible to keep LNB on its place without changing it,if not ,let me know.I can get 55 x 60 dish for completely free from an guy,he offered it to me....So,with that i can be on the horse,therefore,i will save some extra money. 

I can't wait to see your whole assembly proccess.Pls,do not forget to display it.I am trully appreciate your help.

 

Hi you cannot use a LNB for hydrogen line. The LNB is receiving 12 GHz however the H line is 1.4 GHz. So you will need the can made to receive 1.4 GHz.

In the link he is using a very good LNA on the dish with a noise figure of 0.3 dB as well. 

Half the work is in the software using smaller dishes.

For a minimum start I would go for,

1m dish, 20db LNA, 20 dB line amp, dongle and you should be able to detect hydrogen.

This LNA has been used successfully, it's 20db gain and ( important noise figure of 0.6db)

https://www.ebay.co.uk/itm/LNA-50-4000MHz-SPF5189-RF-Amplifier-Signal-Receiver-For-FM-HF-VHF-UHF-0-6dB-UK/263793459193?epid=19021137313&hash=item3d6b50bff9:g:ss4AAOSwiNxbO2sL&redirect=mobile

You will need to put a dish feed together as well.

Happy to help will have a diagram up soon.

Carl

1 hour ago, Coto said:

@Carl Reade Do you know a website/calculator for designing a can feed? I can only find bi-quad calculators.

Hi on this site there is a link to a spreadsheet for the calculations for a can feed horn.

http://www.setileague.org/hardware/feedchok.htm

Carl

2 hours ago, ZijadSarajevo said:

@Carl Reade As you recommended,i hope i picked it properly....

I know i need a dish to nearly 1 meter (diameter),nothing bellow 96 cm...

1.LNA

https://www.ebay.com/itm/0-1-2000MH-z-RF-Wideband-Amplifier-30dB-low-noise-LNA-Broadband-Module-Receiver/311841967599?hash=item489b3acdef:g:KrwAAOSwuLZY57ZS:rk:1:pf:0

2.Satelite line  amplifier 20db

https://www.ebay.com/itm/Satellite-20dB-In-line-Amplifier-950-2150MHZ-Signal-Booster-For-Antenna-AE/382605486101?hash=item5915106815:m:mU717aqYcmk_Qtp-xdJxoQw:rk:1:pf:0

3.I need your sugesstion about these Filters in line....

4.Power suply will not be a problem...

5.SDR donngle...

https://www.amazon.com/dp/B0129EBDS2/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=rsv0f-20&linkId=9806dfa291f74f7cdb49e2cfbe3d34eb

or even this one.....

https://www.amazon.com/dp/B011HVUEME/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=rsv0f-20&linkId=983e9b382e58ce311dbc03b00457d4c1

And best possible guide to assemble all tgoether...

I hope i am not too boring with endless questions...

 

Hi no boring questions at all,

Here is a link for filters at a reasonable price I would use one at least to start with and next to the LNA.

https://redirect.viglink.com/?format=go&jsonp=vglnk_154137269185016&key=e6d017f13f6a6e8cc619287ca1b92ca3&libId=jo3hfox701013trd000TA1f6l0dvz&loc=https%3A%2F%2Fstargazerslounge.com%2Ftopic%2F319651-anyone-doing-hydrogen-line-observing%2F%3Fpage%3D2&v=1&out=http%3A%2F%2Fadsbfilter.blogspot.com%2F2015%2F06%2Fhydrogen-line-1420-mhz-filter.html&ref=https%3A%2F%2Fstargazerslounge.com%2Fforum%2F75-radio-astronomy-and-spectroscopy%2F&title=Anyone doing hydrogen line observing%3F - Page 3 - Radio Astronomy and Spectroscopy - Stargazers Lounge&txt=http%3A%2F%2Fadsbfilter.blogspot.com%2F2015%2F06%2Fhydrogen-line-1420-mhz-filter.html

Your looking a noise figure of 1db or less on the LNA not sure if that one is. If you can get one screened on the board that is also ideal. Wideband LNAs amplify everything.

SDR is fine

Line amps fine

You will also need various connectors, SMA etc

I will put up what I put together soon which should help.

Here is a link which is excellent and helped me a lot with software

http://parac.eu/projectmk3.htm

Carl

42 minutes ago, Coto said:

@Carl Reade I might soon get a 1.5m prime focus dish and was wondering which is more "ideal": a biquad or a can Feed (for 1420MHz)?

As for the LNA, I understand how noise figure affects the sensitivity of the telescope, but what exactly is gain? Higher gain = higher amplification = better?

What exactly do in-line amps do and how do they differ from LNAs?
When you say filters do you mean bandpass filters? If so, isn't a single filter needed? Why would more than one be needed? And where should these be placed in the superheterodyne system?

Which SDR would you recommend? Is it important to look for sensitivity/noise-figure characteristics, or will the LNAs ensure the signal is "strong" enough for the SDR to interpret fine?

Hi, I would think the can type would be better as it would reject interference better but I have not seen a comparison between the two. I decide on the biquad as I had the materials at hand.

Yes LNA it's amplification. As someone once put it, you are making an impossibly weak signal into a rediculisly weak one. The aim is to get the hydrogen line out of the noise.

The inline amps are to eliminate gain loss in the coax and filters and multiple connectors used. The difference between these and LNAs is probably the noise figure which is around 4 dB so no good at the dish but fine for second stage amplifiers.

yes bandpass filters you may get away with one as long as you don't have local interference. The LNA I use is filtered then I have one just before the dongle.

I use the Egoo cheap SDR dongle. From reading they all are around the same noise figure 6db but that is irrelevant to the system noise figure. Would definitely cool it with a heatsink as they get very hot and heat is bad.

15 minutes ago, ZijadSarajevo said:

Hydrogen,strictly...

Ok best advice i would say is,

Get the biggest dish you can! You will likely have to make the dish feed yourself either the the one on this thread or the can type (measurements online).

Next is a good low noise amplifier (LNA). Around 30db gain and the lowest noise figure you can get. This noise figure will be the benchmark for the system.

You will need probably two 20db satellite line amplifiers these are cheap and work fine.

You will need filters in line as well to keep out interference. You can get these on the LNA4ALL site.

You will need a power supply 12V and a DC inserter to power the amplifiers.

You will need a receiver, a SDR dongle is fine

A computer and software.

Once you have a working scope then you can improve it as you go along.

Carl

Hi what sort of observations are you wanting to do, Hydrogen line, sun moon?

You can make a basic radio telescope from the following,

A small dish 50cm.

A universal LNB

An analogue satellite meter

A 12 Volt power supply

This would enable you to take readings from the sun and moon to start with.

1 hour ago, robin_astro said:

Thanks Carl, 

For a filter at that price it hardly seems worth the metal bashing to build one.

(Wow that callsign is almost as old as mine, though I have not been active for many years)

Cheers

Robin

Yea I know I don't have the test gear to make them even. Haven't been on the air myself in a while. I'm guessing there is a build in the pipeline?

Carl

58 minutes ago, robin_astro said:

Hi Carl,

What filtering are you doing before the SDR?  Is it a narrow passband filter specifically tuned to 21cm or is it just something to keep the strong broadcast signals out ?

Thanks

Robin

Hi Robin, it's a specific one made by Radio Astronomy Supplies. I think it was +/- 15Mhz. The label has came off over time. (Photo)

I should also mention the LNA is the SBA1300-1700 from RF Design (G8FEK).

The guy Adam who sells LNA4ALL also now makes H line filters at 20 Euro I have ordered before with him and good to deal with.

http://adsbfilter.blogspot.com/2015/06/hydrogen-line-1420-mhz-filter.html.

Carl

More playing with data and contour graphs the green areas and all within is hydrogen. Even between the two arm sweeps hydrogen is present.

The centre Freq should read 1.420410Ghz.

Carl

Hi all let the scope run from around 17:30 through to 09:30 this morning. This would pick up two sweeps of the galaxy. 

Excel seems to struggle with 3d graphs but managed to put one together. There are two interference bands and in-between them the milkyway peeks. The rear peek is the strongest I have seen so I will check where it passed later.

The gragh is 2.4 MHz wide spectrum over the time period.

Finally the scope is mounted. I knew the concrete pier would be multiple use. Now I can get some proper settings done.

LNA now boxed and single 40mm pipe used for the feed.

1 hour ago, robin_astro said:

Yes I guess it will be tough to pull this out with this beamwidth.  (How about a second dish to do some interferometry ?)  If you are an early riser you could perhaps try for Tau A which is better isolated.  I found this useful chart of comparative signal strengths a while back somewhere on line.  

Robin

Thanks for that Robin. I am pushing my luck with a single dish this size in the garden ?

Yes Taurus is another to look at. I can leave the scope recording 24hrs with the FFT program. Currently I need to get it on a mount so it's easier to set Alt/Az. But its producing good results and lots of data.

Carl

Hi all turned the scope towards Cassiopia for a drift scan not sure if Cas a is in there somewhere but was certainly within the beam. Below is an animation and a still in Cassiopia.

Carl

5 hours ago, Coto said:

What’s your integration time again? And is this the Milky Way? Have you been able to observe anything beyond the Milky Way with the dish?

Also, is 1.2m the long or the short diameter of the dish? Since it’s an offset, the short diameter is the one that should concern you and should be used to calculate antenna Beamwidth etc. (looking at the dish from your target looks like a circle, with the diameter being the shorter diameter of the ellipse, so the beam should be as symmetrical as a Prime Focus dish).

Hi I am averaging in FFT this link should help

http://parac.eu/projectmk4.htm

Yes it's the Milky Way. A drift scan of the arms.

It's a 1.2m dish therefore 1.2m in diameter.

Beamwidth 10-12 deg.

I am currently still fine tuning the system and have not tried to receive anything beyond the galaxy at this time. All the stronger sources outside the galaxy are in the southern hemisphere. If you mean other galaxies I would doubt a dish of this size would be capable, possibly pulsar observations could be achieved. You also have to take into account that radio sources are brighter at other frequencies than 1.4Ghz.

Carl

Hi all here is an animation made from Excel data from last night from 6 pm to around 12am. its a bit crude as the graph auto fits as the signal gets larger. Its around 60x 5min chunks of data. Will need a better way of displaying but work in progress.

The system I think is working beyond what I expected for a 1.2 m dish.

1 hour ago, Coto said:

@Carl Reade Can you check the SDR's operating temperature and try to reduce the temperature down a bit and see if noise is affected? I'd be curious to see if lowering the temperature a bit can really present reasonable improvements to SNR.

Hi Coto unfortunately the dongle is now attached to a heatsink so can't really do a comparison. The chips were running too hot to touch before now they are just above room temp. I have seen them measured at 80deg.

Heat is an enemy with radio so it will help with noise and stability. How much I cannot measure.

I did notice most if not all interference spikes disappeared.

The noise figure at the antenna/LNA sets the benchmark of the system and SNR is more important. The key to these setups are good antennas and the best LNA noise figure you can get hence they are cooled at the antenna in professional radio telescopes.

Carl