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


65 Responses so far.


  1. prachetan potdar says:

    i want to make engineering final year project on SDR ‘titile is” hf converter using SDR” i need your guidance and i want to make this project under 300$ ,
    remember i want to implement prototype of this design

  2. Mario says:

    Hello, do you still have these for sale at 35€ including shipping, fully assembled, without case?
    Have you made any update since this post?
    Please let me know how I can purchase.
    Thanks,

  3. Richard says:

    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.

  4. Nacho says:

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

  5. Ahmed says:

    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,

  6. Jani says:

    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

  7. Jerry says:

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

    • Gary says:

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

  8. Keith Browning says:

    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.

  9. Keith Browning says:

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

    • 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.

  10. Keith Browning says:

    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.

  11. Ben Potter says:

    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

  12. Sierra says:

    Dear Kalle,

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

    Thank you
    Sierra

  13. Ton says:

    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

  14. Lucas Fonseca says:

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

    PY2- BRAZIL

  15. Sri Bintoro says:

    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

    • Lucas Fonseca says:

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

  16. Txema Araluze EA2AFR says:

    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

  17. Johanes Hermanto says:

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

    Johanes

  18. darethehair says:

    Info on your HF upconverter for Canada? Thanks!

  19. Ricky Marsh says:

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

    Thanks

    Ricky

  20. Txema Araluze - EA2AFR says:

    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

  21. Giannis Grammenos says:

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

  22. Lothar says:

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

    Regards 55/73

  23. Dominic says:

    Do you still have any left?

    72

    Dom
    M1KTA

  24. Pravin K says:

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

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

  26. Jaime says:

    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

  27. Dana says:

    I’m interested in this converter if available?

  28. Carlito says:

    I am interested too. Please give me details.

  29. Andrea says:

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

  30. CERA says:

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

    Greetings

    • CERA says:

      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.

  31. Steve Smith says:

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

  32. Gm0lze says:

    Are there any converters still available.Thank you.

  33. Gm0lze says:

    Really nice design.Do you have any available ..

    GB3IG.

  34. Jon says:

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

  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

  36. millot daniel says:

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

  37. millot daniel says:

    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)

  38. andoras says:

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

  39. David KB6QMX says:

    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.

    • 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.

  40. Luis Felipe says:

    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.

  41. Lyndel, N7LT says:

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

    Tnx es 73
    Lyndel, N7LT

  42. David Gilpin says:

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

  43. Benjamin says:

    Hi,

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

    Happy New Year!

  44. Gerry Jannetta says:

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

    Regards Gerry (G4 NYC)

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