Review of the SpyVerter Upconverter

The SpyVerter is a new upconverter that has recently gone on sale. It is created by Youssef (creator of the Airspy SDR and programmer of SDR#) and Bob W9RAN (of rantechnology.com and youtube.com/user/ranickel). In this post we’ll review the SpyVerter and compare it against some other up converters that we have used in the past.

Background

Radio transmissions between 0 – 30 MHz can travel all the way around the world. At these frequencies many interesting signals such as international shortwave radio, ham radio communications and several military transmissions exist.

The RTL-SDR’s lowest tunable frequency is 24 MHz, and so it can only receive a small portion of the interesting transmissions that occur between 0 – 30 MHz. In order to listen to frequencies below 24 MHz an upconverter is required (either that or perform the direct sampling mod). An upconverter works simply by shifting these lower frequencies up to a higher frequency that the RTL-SDR can receive. For example, a 5 MHz signal might be upconverted to 105 MHz.

To date, most decent upconverters (such as the popular ham-it-up upconverter) have been based on the double balanced mixer architecture implemented by the ADE-1 mixer chip from Minicircuits. The SpyVerter on the other hand is based on a different type of architecture which is inspired by the H-mode mixer design that was used in the unreleased HF7070 communications receiver. The expected major advantage that this design has over a ADE-1 based design is better IIP3 performance. This essentially means that strong signals will not cause overloading issues in the SpyVerter, meaning less noise and spurious images.

Another advantage of the SpyVerter is its use of a 120 MHz low phase noise/low jitter clock, meaning less reciprocal mixing and thus greater SNR and a lower noise floor. A low phase noise clock is essential for getting good performance when receiving the very narrowband signals that are typically found between 0 – 30 MHz. The other upconverters do not specify their phase noise performance as far as we can tell.

The SpyVerter comes in a metal box, with three SMA adapters. A metal box is great because it helps keep strong interfering signals from entering the signal path, as well as stabilizing the internal temperature, keeping frequency drift to a minimum. Most upconverters only come with a metal box as a paid add on, but the SpyVerter comes in one by default.

Although the SpyVerter is designed to be used with the Airspy, it is fully compatible with the RTL-SDR as well. The SpyVerter can be powered via a USB cable, or via 5V bias tee (and this is compatible with the bias tee used on the RTL-SDR Blog units sold by us).

The SpyVerter in enclosure with bundled adapters.

Spec Comparison

Unit	Clock	Bias Tee?	LNA?	Architecture	Enclosure?	Extras?	Price (USD)
Spyverter	120 MHz, low phase noise	Yes	No	H-mode mixer inspired	Yes, in metal box by default.	Three adapters.	$59
Ham-It-Up	125 MHz	No	No	ADE-1 (v1.0) / ADE-1 Reversed (v1.3+)	Available as extra add on.	Optional noise source circuit (not populated by default)	$44.95 + enclosure $21.95
Nobu	100 MHz	No	No	ADE-1 Reversed	Available as extra add on.	None.	$56 + enclosure $25
SV1AFN	200 MHz	No	Yes	ADE-1 Reversed	None available.	None.	$57

Testing

The creators of the SpyVerter, Youssef and Bob (W9RAN), sent us a unit for review a few weeks ago and below we present some real world test results. We compare the SpyVerter against two ADE-1 based designs. A Ham-It-Up V1.0 and an upconverter designed by Nobu of Japan. The ham-it-up V1.0 uses the ADE-1 in a standard configuration, whereas Nobu’s upconverter uses the ADE-1 in reverse. Using the ADE-1 in reverse allows better operation near DC, but can create impedance mismatch problems. If you want more info about this, see this post where Mile Kokotov reviews the SV1AFN (also uses the ADE-1 in reverse) and the ham-it-up and discusses a bit about the ways the ADE-1 can be connected. We note that newer versions of the ham-it-up (v1.3) use the ADE-1 in reverse as well, so the performance of a modern ham-it-up may be closer to that of Nobu and SV1AFN’s design.

In each of these tests we used an RTL-SDR Blog dongle, SDR# and the special decimation driver for the R820T released by Vasilli. Vasilli’s decimation drivers make viewing HF signals in SDR# much more pleasant as it allows for a high resolution decimated zoom and thus improved visual SNR. This makes spotting narrowband weak signals much easier. His plugin also has a “Use SpyVerter for HF” option which simply automatically sets the correct frequency offset value of -120 MHz for the SpyVerter. Each upconverter was powered by an external battery pack.

The testing was performed sequentially, but all three units were tested within 5 minutes to ensure that HF conditions did not change too much. All tests used a roof mounted Miniwhip antenna (except for one test which used a Magnetic Loop).

Spyverter vs Nobu’s Upconverter vs Ham-it-up

AM Broadcast Band

Here we tested all three units on the AM broadcast band between DC and 2 MHz. Gain settings were kept the same for all tests.

Miniwhip

From these comparison images it is clear that the SpyVerter has the lowest noise floor and highest SNR on the signals.