Aerial for SDR radio

[pistonheadforum]

Anybody know anything about SDR radios?

Looking for an internal ariel to cover as wide a range of frequencies as possible for an RSPdx SDRplay - https://www.sdrplay.com/rspdx/

Reading online it's hard to get a definative review so wondered if the PH masive had any opinion/experience on these:

https://www.amazon.co.uk/Moonraker-Skyscan-Desktop...

https://www.amazon.co.uk/Moonraker-Skyscan-Mobile-...

It would be inside mounted in the attic as I can't have an outside ariel.

Thanks in advance.

[Paul Drawmer]

Any indoor antenna to receive the whole of the radio spectrum is going to be compromised.

I would suggest that you get an antenna which covers that part of the spectrum that you are interested in. Otherwise, just plug a wire in.

[pistonheadforum]

Thanks - appreciate the reply.

Yup, it's gonna be a compromise but it's just a bit of experimentation to see what is out there and I'm interested in all areas of the spectrum at the moment.

Think I'll take a punt on the larger one.

[anonymous-user]

An antenna from 1kHz to 2GHz with any kind of useful performance does not exist, you will need a range or be selective in what you wish to look at.

You can get 30MHz to 2GHz antennas but are huge and expensive, used for things like EMC testing such as this but it is expensive.

https://www.theemcshop.com/ah-systems-emc-biconica...

For the higher frequencies you make dipoles out of coax and experiment a little with the magic that is antenna theory.

[steve-V8s]

An ideal antenna will be resonant on the frequency you want to listen to. This makes it more receptive to that particular frequency whilst rejecting signals (or noise ) you would prefer not to present to the receiver. An antenna can be designed to work on harmonically related frequencies but even that will be a compromise. Trying to use one system for a very broad range will be very poor because a) it will be the wrong length for almost all of the spectrum and b) the impedance at the end of the antenna will not match the receiver input over most of the spectrum.

You can partially resolve the impedance issue by connecting the antenna via a matching unit but it will still be a compromise.

[pistonheadforum]

Thanks.

I'm always amazed when people just say make your antenna from a bit of speaker wire and an old bin lid (or something equally random)!

Apprecaite that a harmonic dipole is the best thing with the length tuned to the frequency that you want to focus on.

Everytime I've made an ariel it's had all the receiving ability of a cheese sandwich.

Anyhoo ... I've ordered the desktop one linked above so we can see what happens.

[anonymous-user]

pistonheadforum said:

Thanks.

I'm always amazed when people just say make your antenna from a bit of speaker wire and an old bin lid (or something equally random)!

Apprecaite that a harmonic dipole is the best thing with the length tuned to the frequency that you want to focus on.

Everytime I've made an ariel it's had all the receiving ability of a cheese sandwich.

Anyhoo ... I've ordered the desktop one linked above so we can see what happens.

The truth is you can make antenna from a bit of soeaker and a bin lid, trouble is might not be any good. Many cars in the 70's used an old metal coat hanger as an ariel when the rod one got snapped off.

[steve-V8s]

You can fabricate a perfectly functional antenna out of speaker wire or a coat hanger provided it is cut to the correct length for the frequency you are interested in.

[eliot]

A discone antenna will receive a wide range of stuff to get you started.

Realistically the interesting stuff is around 120-145 Mhz (civil aircraft to 2m ham band) and 430-446 (70cm's ham band to PMR licence free). A "2/70" ham co linear will such as a diamond v2000 will work reasonably well.

I have a 2/70 diamond v2000 on my roof and if you ask nicely i can fire up my raspberry pi that runs spyserver and then you can connect to it via TCP/IP from a local copy of SDR Sharp and listen to what's going on in the Newport Pagnell Area. You can listen to the motorway crews on using a DMR decoder plugin.
Even managed a few NOAA weather sats on the discone irrc.

There is some stuff around 150-180 such as taxi's and pagers.

Anything under 30mhz will want a long wire antenna (or use the online SDR's)

I started out on SDR radio - specifically Airspy & SDR# then went ahead and passed my HAM licences - but lost interest since then.

m0mez.

[pistonheadforum]

eliot said:

A discone antenna will receive a wide range of stuff to get you started.

Realistically the interesting stuff is around 120-145 Mhz (civil aircraft to 2m ham band) and 430-446 (70cm's ham band to PMR licence free). A "2/70" ham co linear will such as a diamond v2000 will work reasonably well.

I have a 2/70 diamond v2000 on my roof and if you ask nicely i can fire up my raspberry pi that runs spyserver and then you can connect to it via TCP/IP from a local copy of SDR Sharp and listen to what's going on in the Newport Pagnell Area. You can listen to the motorway crews on using a DMR decoder plugin.
Even managed a few NOAA weather sats on the discone irrc.

There is some stuff around 150-180 such as taxi's and pagers.

Anything under 30mhz will want a long wire antenna (or use the online SDR's)

I started out on SDR radio - specifically Airspy & SDR# then went ahead and passed my HAM licences - but lost interest since then.

m0mez.

Thanks for this - very interesting.

I thought an SDR would give the greatest flexility (plus SDRUno looks cool!).

Is there any benefit to getting something like a Uniden UBCD3600XLT for out on the field, or are these unable to pickup anything more than you can get with a Uniden UBC125XLT?

There is the Uniden SDS100E but that's a fair bit more - are these worth it do you think?

Many thanks.

[Dr Jekyll]

pistonheadforum said:

Thanks for this - very interesting.

I thought an SDR would give the greatest flexility (plus SDRUno looks cool!).

Is there any benefit to getting something like a Uniden UBCD3600XLT for out on the field, or are these unable to pickup anything more than you can get with a Uniden UBC125XLT?

There is the Uniden SDS100E but that's a fair bit more - are these worth it do you think?

Many thanks.

Unless you are doing something very specialised then no advantage in the 3600XLT over the 125, it doesn't receive any better and it's more complicated to use.

[rxtx]

Dr Jekyll said:

Unless you are doing something very specialised then no advantage in the 3600XLT over the 125, it doesn't receive any better and it's more complicated to use.

There is a big advantage in that it decodes digital modes, and the majority of services are now using DMR.

[rxtx]

OP, don't buy either of those antennae, they are crap and you'll just replace them. Moonraker's returns policy is also next to nonexistent, they won't even honour your statutory rights unless you really push them - I speak from experience and won't touch them.

You'd be best off either making your own J-antenna or buying a colinear and sticking to VHF/UHF for the time being. With the SDR you can use a digital decoder if you don't mind jumping through some hoops. Do that before you invest a fair chunk in a decent scanner. There is not much to listen to on analogue FM nowadays.

FWIW I use a fully loaded SDS100 for scanning and it is very good, better than the 3600. I have a full amateur licence and it sits alongside my transceivers.

[pistonheadforum]

rxtx said:

OP, don't buy either of those antennae, they are crap and you'll just replace them. Moonraker's returns policy is also next to nonexistent, they won't even honour your statutory rights unless you really push them - I speak from experience and won't touch them.

You'd be best off either making your own J-antenna or buying a colinear and sticking to VHF/UHF for the time being. With the SDR you can use a digital decoder if you don't mind jumping through some hoops. Do that before you invest a fair chunk in a decent scanner. There is not much to listen to on analogue FM nowadays.

FWIW I use a fully loaded SDS100 for scanning and it is very good, better than the 3600. I have a full amateur licence and it sits alongside my transceivers.

Thanks for this - a bit late though!

I do fancy learning to make antennas so this will make a good reference - if the ones I build are better then it shows I'm heading in the right direction!

[Dr Jekyll]

rxtx said:

OP, don't buy either of those antennae, they are crap and you'll just replace them. Moonraker's returns policy is also next to nonexistent, they won't even honour your statutory rights unless you really push them - I speak from experience and won't touch them.

You'd be best off either making your own J-antenna or buying a colinear and sticking to VHF/UHF for the time being. With the SDR you can use a digital decoder if you don't mind jumping through some hoops. Do that before you invest a fair chunk in a decent scanner. There is not much to listen to on analogue FM nowadays.

FWIW I use a fully loaded SDS100 for scanning and it is very good, better than the 3600. I have a full amateur licence and it sits alongside my transceivers.

That's useful to know. Is there much to listen to on DMR?

[rxtx]

pistonheadforum said:

Thanks for this - a bit late though!

I do fancy learning to make antennas so this will make a good reference - if the ones I build are better then it shows I'm heading in the right direction!

Sorry for my tardiness

Dr Jekyll said:

That's useful to know. Is there much to listen to on DMR?

It all depends where you live, but the short answer is yes. Ofcom list all the licences and frequency allocations in their Wireless Telegraphy Register, you can download the CSV here:

https://www.ofcom.org.uk/spectrum/information/spec...

I wrote a script that downloads it and loads it into a database, and another that generates a KML file centred on a lat/long which shows all licences within a specified radius for loading into Google Earth. If I'm going somewhere I'll do that and program the scanner accordingly.

Remember you're not supposed to listen to this stuff

[eliot]

rxtx said:

I wrote a script that downloads it and loads it into a database, and another that generates a KML file centred on a lat/long which shows all licences within a specified radius for loading into Google Earth. If I'm going somewhere I'll do that and program the scanner accordingly.

Remember you're not supposed to listen to this stuff

small world - i’ve used that kml file.

[rxtx]

eliot said:

small world - i’ve used that kml file.

Not the one generated from the script I wrote I don't think since I've only sent it to one other person, and it was centred on Watton-at-Stone There are so many licensees in the WTR even my one for "25 mile radius from Hertford" brings Google Earth to a virtual halt due to North London.

[pistonheadforum]

Thanks!

I have to say this just makes me want to get an UBCD3600XLT even more for field work!

[pistonheadforum]

Sounds like the SDS100E is the more modern one, but the fact it does not take standard AAs is a bit of a downgrade for the more ocassional user.