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HF converter for SDR radios

Posted by Kalle Hyvönen Posted on Dec - 10 - 2012

I wanted to listen to HF bands using my RTLSDR USB dongle. Since the RTLSDR dongle can only receive from around 64MHz upwards I needed an up-converter which converts the HF band (0-50MHz) to a higher frequency I can receive with my dongle. The converter will work up to about 70MHz.

Many of the available converters seemed quite pricey and not too well designed (no filtering on the local oscillator etc.) so I decided to make my own.

The converter is fairly simple, it consists of an elliptic low-pass filter on the input, a local oscillator with a band-passfilter, a mixer and a Butterworth band-pass filter on the output. The converter takes in a signal in the 0-50MHz range and mixes it with the 100MHz local oscillator, yielding a 100-150MHz signal you can receive with an RTLSDR dongle.

After quite a bit of reading filter design books and simulating this is what I ended up with:

HF converter schematic

HF converter schematic

If you’re wondering why the signal is going in to the “IF out” pin of the mixer; it’s not a mistake. This is a small trick you can use to extend the frequency response lower when you are up-converting.

The mixer I used is an ADE-1 from Mini-circuits and the local oscillator is an ASEM series oscillator from Abracon (100MHz +-50ppm model).

I ordered the PCBs from iTead:

Finished HF converter

Finished HF converter

Few HF converters with an RTLSDR dongle connected to one

Few HF converters with an RTLSDR dongle connected to one

Here is a 0-50MHz (-30dBm) sweep on the input and spectrum analyzer connected to the output:

0-50MHz conversion sweep, input -30dBm

0-50MHz conversion sweep, input -30dBm

Here is a 10-150MHz sweep of the elliptic Cauer low-pass filter on the input:

50-150MHz sweep of the input Cauer low-pass filter

50-150MHz sweep of the input Cauer low-pass filter

This equates to around 9dB conversion loss (typical for a ring diode mixer) with around few dB ripple on the passband so I’m pretty happy with it! There is about -51dBm of LO leak on the output which is also quite low.

I did some testing by unwinding a few meters of wire from a roll and used that as an antenna and this worked really well. Lots of signals to listen to!

The converter is designed so that it should fit to one of these (just need to cut the box a bit shorter):

Box for the HF converter

Box for the HF converter

I have a few of the converters left if someone is interested in one! You can contact me at kalle.hyvonen ^AT^ dgkelectronics.com

edit: Added a picture of a 10-150MHz sweep on the input low-pass filter

Categories: Electronics projects, HF converter, SDR radio

62 Responses so far.

  1. Richard says:
    27/12/2013 at 18:24

    I have just bought a RTL-SDR USB dongle and was looking for an up converter when I found this page. I am particularly attracted to your design because you filter the oscillator as well as the input and output.

    I see that your original post was a year ago and I wonder whether you have any of the PCBs left or even complete kits. Please email me when it is convenient.

    73, Richard.

    Reply
  2. Nacho says:
    10/10/2013 at 12:06

    Hi,
    I’m interested in your hf upconverter. Can you tell me details about order to Spain? Thank you.

    Reply
  3. Ahmed says:
    01/10/2013 at 13:18

    Dears

    I am interested in your HF converter for SDR and I would like to buy assemled one.

    How to order and how much does is cost.

    Regards,

    Reply
  4. Jani says:
    28/07/2013 at 02:16

    Hi Kalle,

    I’m new to exploring the signal environment with my dongle. Currently I’m using gqrx on Linux using using some lame antenna for broadcast frequencies.

    Do you have HF convertes still “in stock”? I’m interested to buy one.
    Also I’m interested either the drawings of your Discone antenna or the “assemble yourself” (http://www.dgkelectronics.com/discone-antenna-for-rtlsdr/).

    As you see, I’m totally out of conversation when talking about deep technical thingies, but still wanting to explore things.

    Br,

    Jani

    Reply
  5. Jerry says:
    19/07/2013 at 19:32

    Do you have any upconverters for the rtlsdr dongles and if so how much?

    Reply
    • Gary says:
      19/08/2013 at 23:33

      Hi just would like to know if you have any kits left and if how much
      many thanks Gary from the uk

      Reply
  6. Keith Browning says:
    09/06/2013 at 01:19

    I had not considered the input low pass filter in your design. It will attenuate the FM band signals from the antenna and that will be sufficient in most cases.
    Good shielding should fix the extreme cases where FM signals get into the “IF”.
    I needed to think first, before replying to your blog.

    Reply
  7. Keith Browning says:
    07/06/2013 at 12:44

    I should have added. I really like the design and would like to get a board, if the Oscillator can be changed .

    Reply
    • Kalle Hyvönen says:
      08/06/2013 at 07:24

      Hey Keith! I did think about this but it seemed like people weren’t having problems with using a 100MHz oscillator so I decided to use one as well. You can get the ASEM-series oscillators up to 150MHz so swapping it for a higher frequency one is easy. You just need to recalculate the band pass filter for the oscillator.

      Reply
  8. Keith Browning says:
    07/06/2013 at 12:39

    In a lot of places, it would be better to have a higher frequency oscillator, say 120MHz so the output avoids the FM broadcast band.
    Alternatively an FM band stop filter might help.
    I think the higher frequency is easier.

    Reply
  9. Ben Potter says:
    03/06/2013 at 22:47

    This looks like just the thing for a complete HF beginner like me, thank you! Have you any left, please? I am in the UK.

    Many thanks,

    Ben

    Reply
  10. Sierra says:
    28/05/2013 at 02:47

    Dear Kalle,

    I’m interested inpurchasing your converter. Please get back to me through email.

    Thank you
    Sierra

    Reply
  11. Ton says:
    27/05/2013 at 18:40

    Dr Kalle

    Do you still have the HF upconverters?
    Could you email me the detail how to get one?

    Thank you very much in advance.

    Greetings from the Netherlands.

    Ton

    Reply
  12. Lucas Fonseca says:
    22/05/2013 at 06:09

    Like to of these a converter accepts payment by paypal SDR’m from Brazil and here is still a novelty for many.

    PY2- BRAZIL

    Reply
  13. Sri Bintoro says:
    24/04/2013 at 09:49

    Hello, i am from Indonesia.

    Do you have some for sale and what’s the price for it including post & package to Indonesia?

    Sri Bintoro

    Reply
    • Lucas Fonseca says:
      22/05/2013 at 06:08

      Like to of these a converter accepts payment by paypal SDR’m from Brazil and here is still a novelty for many.

      Reply
  14. Txema Araluze EA2AFR says:
    23/04/2013 at 20:23

    Dr Kalle
    Please let me know if still not availability of your UP_converter. I’m waiting for some time because even there in the market are msome other units I like very much yours.
    So if there is the oportunity to get 3 units, please, let me know.

    Thank you very much in advance. Greetings from Basque Country.

    Txema – EA2AFR

    Reply
  15. Johanes Hermanto says:
    13/04/2013 at 00:07

    Hi,
    Do you still have the upconverters? Could you email me the detail how to get one, please? Thanks.

    Johanes

    Reply
  16. darethehair says:
    09/04/2013 at 16:33

    Info on your HF upconverter for Canada? Thanks!

    Reply
  17. Ricky Marsh says:
    22/03/2013 at 02:19

    I do still have the filters for sale, if so how much delivered to the UK.

    Thanks

    Ricky

    Reply
  18. Txema Araluze - EA2AFR says:
    16/03/2013 at 11:05

    Dr Kalle
    Looking around for some infos concerning to an up_converter for my RTLSDR dongle I found you.
    First of all I must say I’m a newcomer (or better said a perfect NULL on that) and I’m doing my vey first steps. searching for a not very expensive device I’ve found the info referred at your converters. Now the question is that:

    Still having this converters (at least one of them) ?.
    If that’s OK, please, let me know how much money is it and what to do for sending you the money (Bank account, PyPal, etc.).

    I thank you very much in advance and, please, excuse me but I can’t do better with my “Spanglish” HI HI.

    Greetings from Spain

    Reply
  19. Giannis Grammenos says:
    12/03/2013 at 10:26

    Hi,
    Do you have any of the kits available
    Can you give me price and shipping for Greece
    Thank you

    Reply
  20. Lothar says:
    08/03/2013 at 10:13

    >Hello,
    do you have still some for sale and whats the price for it including post & package to Germany?

    Regards 55/73

    Reply
  21. Dominic says:
    05/03/2013 at 16:04

    Do you still have any left?

    72

    Dom
    M1KTA

    Reply
  22. Pravin K says:
    28/02/2013 at 14:14

    Hi,
    Do you have any of the kits available for sale?
    Please send pricing if available.

    Reply
  23. Round-Up of RTLSDR Upconverter Choices | KF7LZE's Blog says:
    26/02/2013 at 05:46

    [...] Kalle over at DGK Electronics has a great looking compact 100MHz HF converter / upconverter designed to fit inside of a pre-made [...]

    Reply
  24. Jaime says:
    21/02/2013 at 16:31

    From Portugal and I’ interesed in one of this sdr converter,do you sell to portugal if so, how much ,include postal.

    Many thanks

    CT1ESU Jaime

    Reply
  25. Dana says:
    21/02/2013 at 02:26

    I’m interested in this converter if available?

    Reply
  26. Carlito says:
    16/02/2013 at 03:37

    I am interested too. Please give me details.

    Reply
  27. Andrea says:
    12/02/2013 at 00:59

    Hi,
    I’m interested in your hf converter. Can you give me price and shipping for Italy? Thank you.
    Bye.

    Reply
  28. CERA says:
    11/02/2013 at 13:30

    Hello,
    We have an idea of the price with shipping cost for France?

    Greetings

    Reply
    • CERA says:
      11/02/2013 at 14:46

      I’m finally interested for an order of one or two converters.
      I would like to know what manner I can pay you.
      Credit card, check, or other.
      For information I live in France in Paris.

      Reply
  29. Steve Smith says:
    08/02/2013 at 09:12

    I am interested in one of the converters as well, thanks and 73.

    Reply
  30. Gm0lze says:
    05/02/2013 at 09:21

    Are there any converters still available.Thank you.

    Reply
  31. Gm0lze says:
    05/02/2013 at 09:06

    Really nice design.Do you have any available ..

    GB3IG.

    Reply
  32. Jon says:
    03/02/2013 at 16:06

    Hi,
    If these are available to buy please can you email detail.
    Did you test the low end response?
    Many thanks
    Jon

    Reply
  33. Dave Richards AA7EE says:
    17/01/2013 at 22:35

    Kalle –

    I sent you an e-mail. Am interested in this HF converter. I especially like the fact that you used a diode ring mixer instead of the NE602 device that is used for the mixer in most of the other similar designs I have seen.

    Dave
    AA7EE
    Oakland, CA.
    USA

    Reply
  34. millot daniel says:
    04/01/2013 at 00:26

    Oh, i forgot to ask you how to order your hf converter for sdr
    Thank you
    Daniel F6FTC

    Reply
  35. millot daniel says:
    04/01/2013 at 00:17

    Happy new year from france
    I’m interested by your hf converter for sdr,can you please give me its price and shipping for france (burgundy)

    Reply
  36. andoras says:
    02/01/2013 at 18:52

    hello and happy new year from France ! what’s the price in euro of this hf converter please ?
    thank you.

    Reply
  37. David KB6QMX says:
    01/01/2013 at 09:38

    I am interested in a HF converter for my RTL2832 dongle. After reading the latest edition of QST I am interested in setting up SDR for the first time and trying it out. Will your converter do what the article says without me having to make the converter for the amateur bands? Will it cover 160-6 meters with a Newsky TV28T USB DVB–T & RTL-SDR Receiver? If it will work then I am interested in purchasing one from you. Happy New Year and thanks for your reply.

    Reply
    • Kalle Hyvönen says:
      01/01/2013 at 18:13

      Hey David! My converter should work just fine with any SDR-radio (or any radio for that matter). It will cover about 0.5-70MHz (most likely even lower than 0.5MHz, I will measure this soon) so it will work just fine on the the 6-160 meters range.

      Reply
  38. Luis Felipe says:
    30/12/2012 at 21:52

    Hi, I’m interested in one of your Hf converters, I wonder if you still have, and what is your price to send it to Spain.
    Season Greetings and thanks in advance.
    Luis.

    Reply
  39. Lyndel, N7LT says:
    26/12/2012 at 06:08

    Hello, I’m also interested in one of your smart looking converters, do you still have them?

    Tnx es 73
    Lyndel, N7LT

    Reply
  40. David Gilpin says:
    25/12/2012 at 06:57

    Please advise how may order and how much. Very interested. Thanks. David

    Reply
  41. Benjamin says:
    24/12/2012 at 01:47

    Hi,

    Do you have any of these left? Shipping to the UK.

    Happy New Year!

    Reply
  42. Gerry Jannetta says:
    14/12/2012 at 14:37

    Hi, I am interested in one of your Hf converters.
    How much to purchase one please.

    Regards Gerry (G4 NYC)

    Reply

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