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Re: LF: SDR programs

To: "[email protected]" <[email protected]>
Subject: Re: LF: SDR programs
From: M0FMT <[email protected]>
Date: Tue, 26 Jun 2012 01:08:18 +0100 (BST)
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Hi Graham
OK a subtle point AM is a "Transparent" mode FM is a "Capture" mode and as such not suitable for AC use where simultaneous transmission can block calls. Small random offsets in carrier frequency cause hetrodynes that alert ATC of the presents of a weaker call. Nothing in Marine is ever that immediate so I guess it was expedient to opt for the El-Cheapo FM solution there can be no other reason. Probably a bunch of Civil Servants were conned into believing AM stood for Ancient Modulation.
You are right there are lot of extras that could be added to SDR software and perfectly feasible we just need to learn to programme and add all the goodies we think are needed or find a friendly software jockey to do it for us...... hee!
As far as up converters go the ubiquitous chip is the multiplex FST3253 used in Softrock and other well known up-converters for RX and TX switched with a 90 degree phase shift LO from a pair of 7474 flip flops is the basis for most current SDR detectors or TX mixers. There are now relatively cheap A/D converters which give a wider BW than the are currently available Sound Card solution. And now its all being integrated onto a single IC so your comment earlier about a USB stick TX is with us. It just needs a mass market for the price to come right down and I guess it comes through the Mobile Phone market. 
Big bang doesn't frighten me all bottles here matey retro shack thermionic not thermonuclear.
You'll be telling me next that the Moons gravity bends light ergo radio waves?
It's late!!!
73 es GL Pete M0FMT IO91UX
From: Graham <[email protected]>
To: [email protected]
Sent: Monday, 25 June 2012, 23:38
Subject: Re: LF: SDR programs

R Pete
Ahh   By  split , I mean the  anti-jam   in channel  split  , When  on the  same  frequency, the  ground  TX  (used tobe ?)   off  set  from the  aircraft  Tx  frequency  , so  if the  Aircraft TX jammed  'ON' then  other  aircraft  could  still  receive  the  ground   , that  was  the  reason  for  wide  IF pass  bands and  keeping  to AM  for the  comm.'s ....  Marine  coms  , adopted  FM ...
There is a  afc  for  cw
OT ?  over the  top  more like ,  the  disclaimer on the  yab-a-dab-a-doo  group    is bigger  than the  space  left  for the  messages , I think the  name  Black-Sheep  seems  to  be  quite  apt  now  !,
Big-bang  , according  to  my  arrl  hand  book , HF communications  will  tend to  be  attenuated  in the  direction  of the  burst  , assume  by  producing  quite  a big  Fariday   screen , also  recommends  you  keep  your  radio  in a  metal  sweet tin ala   blue peter  garden ! 
Did  get  good  signals  on the  MW on the  way  to  work  from  France  during  the  eclipse some  time  ago  , due to the  lack  of  ionisation

From: M0FMT
Sent: Monday, June 25, 2012 10:02 PM
Subject: Re: LF: SDR programs

Hi Graham
............ to monitor off frequency nets and the tower/aircraft split............... ? there is no split frequency working the Tower and A/C both use the same QRG its just that the A/C being at altitude can be heard the Tower being low and beyond your radio horizon can not be heard........ if thats what you ment.
I use the say (A) LO for Approach and then say (B) LO for Tower so when the hand over from Approach to Tower occures I merely click the appropriate LO A or B. Usually a 3 to 4 meg shift, well it is at Luton AP anyway.
Sorry wrong end of the spectrum for this reflector........ just as well the RSGB attention is with the Yahoo mess otherwise we may be getting our keying fingers rapped!!!!!!
73 es GL Pete M0FMT IO91UX
From: Graham <[email protected]>
To: [email protected]
Sent: Monday, 25 June 2012, 21:19
Subject: Re: LF: SDR programs

Yes I think  Andy  gave a talk  at the  egham  convention  on using   a/d  from  mobile  phones , the  new  ones had the  extra  bits  to  give the  full  dynamic  range on  HF ..he  was  using   hardware  block  convertors ......... never  saw  any  items  offered  for  sale  ........only  some  very  high price  'HF rx'  using  the  same  ideas  ...I think  the  give  away  is  the  band  being  covered in frequency   blocks , which I assume  is  down to  the  down  convertors
Dont  think  he is  monitoring  BS now , or  we  might  of  got the  fill  in, but  one things  is  certain, the £10 , wonder-dongle  has  saved  me  from  buying  a  R7000 ...All we  need  now  is  a  little  more  stability  in the   control  software  and  a  wide-band  FM option in  HDSDR 
Im getting the  gb3ang   beacon  on  70 Mhz  good  signal  with  my indoor   2 ele  quad .......... the  PMR band  on  446 Mhz  with the  co-linera  from  10 miles away in liverpool  ssb on 144 MHz  etc 
Definable  FM-AFC  (AND  AM)    would be handy  to  monitor  off  frequency  nets  and the  tower/aircraft   split
I think  possible  the  driver  software  could  improve  as  more  take  up  the  idea  ....... could  HDSDR have  its  own  driver  code  block  .......... Ive  noticed there  is a  routine  that  some  times  appears  that  'purges'  the  device  if that  could  be  run at   will  , that  would  be a big  help, to  recover  a  locked   system
73 -G.
From: M0FMT
Sent: Monday, June 25, 2012 8:58 PM
Subject: Re: LF: SDR programs

Hi Bob
If you are directing that mail to me then you need to look at earlier posts.
However if you are a cheque book Ham then it will be of little interest to you.
You say dangle we say dongle..... :-0
These are TV front ends that use the SDR principle and plug straight into your USB port on your Lap top. Normally they are for recieving local digital TV and radio plus a FM band as well. They are available in the US and they can be made to tune from about 60megs to about 1.7gigs. If I need to tell you more please ask but this is all in public domain on the web (but not in Ham mags, at least not in UK). I have played with these things for about 6 months now and for a few quid (dollars) are fun. If you build a simple up converter with a say a 60meg LO guess what, you have an all band HF radio as well.
Oh and BTW I was not entirely sure what Tracy was getting at below?? We are talking 10 dollars not 300+dollars.
73 es GL Pete M0FMT IO91UX
From: "[email protected]" <[email protected]>
To: [email protected]
Sent: Monday, 25 June 2012, 19:34
Subject: Re: LF: SDR programs

Been Kinda out of any loop on this  
if what I read,, if I connect a TV tuner usb dangle witht he correct chip set
it will cover MF to HF using  an appropriate program. I use HDSDR with my SDR IQ
which I like for general reception. So by using the proper chip set HDSDR
will run that TV dangle as a HF radio
On Thu, 21 Jun 2012 22:31:00 +0100 "Tracey Gardner" <[email protected]> writes:
Hello Pete
If we're talking about low priced SDRs, there is a relatively new kid on the block in the form of the Afedri SDR-Net from Israel.
It is what I will refer to as a "proper" SDR i.e. a direct sampling digital down conversion SDR.
It covers 100kHz to 30MHz, has a maximum bandwidth of 1.25MHz and has a LAN interface for remote access.
The best bit is that it costs just over £200 inc shipping and VAT.
You can find more details here
I've no connection other than being a satisfied customer.
73s Tracey G5VU
----- Original Message -----
From: M0FMT
Sent: Thursday, June 21, 2012 9:55 PM
Subject: Re: LF: SDR programs

Hi Mal
The whole reason these things are getting so much attention is the price and the fact they are independent of a sound card or A/D converter. They are not really suitable for or give any advantage on LF because you need an up converter in front. A Softrock SDR with a good sound card will out perform these sticks at MF/LF.IMHO I don't think its worth persuing to be honest. However I think with the DVB-T sticks people have been opening them up to look at the SMT chip marking if not sure. It looks like they don't erase the markings like some well known LF TX suppiers do. Oh and the software plug-ins are only for the RTL2832 chipset.
73 es GL Pete M0FMT IO91UX

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