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Informations about: Hydra, the 10 Ghz Frontend
Update Jan 2, 2021

DUBUS 3/2020 was released in Sept. 2020.,

10 Ghz Extension for Adalm-Pluto(tm)
(To subscribe to DUBUS, the bilingual magazine for the serious VHF and up operator,
click here: www.dubus.org)

....on this page you will find news, bonus material, FAQ and more...

What is Hydra?

"A 10 Ghz Extension for Adalm-Pluto(tm)"
Hydra is a minimal 3cm band frontend, enables you to use FM/CW also on 10Ghz.
The size of the PCB is made for a fit on the ADALM PLUTO (tm by Analog Devices)
which is also called PlutoSDR. Hydra originated from one developments for
El Cuatro, the multiband UHF/SHF receiver, see link below.

NEWS about Hydra V2/V3/V4, and different versions:

NEW: now shipping Hydra V4 with 10mW power output.
All versions have the following in common:
Doubler for 5-> 10Ghz, LNB for receiving, controls for +5V TX and +5V RX.
2 SMA male connectors fit on the ADALM-PLUTO, distance of the plugs (center to center)
is about 23.5mm. The 2nd SMA plug needs to be mated with your PlutoSDR, because the
distance of 23.5mm differs a small bit. Supply current is less than 200mA on TX, and
less than 75mA on RX. Antenna output is on SMA female.

Prelimary Specifications:

TX Power: V3: 5mW V4: 10mW
Fundamental feedthrough (5.184GHz input to 10.368Ghz out): -40dbc
RX noise Figure: V2: 10-13db NF, V3, V4: 10db NF
RX frequency tolerance: 0.25ppm
Supply Voltage: 5V (+0 -0.5V)
Supply Current TX: up to 220mA
Supply Current RX: up to 75mA

Hydra V1/V2:

as described in DUBUS 3/2020, V1 is sold out.
Hydra V2 features one additional TX amplifier, available on request.

Hydra V3:

Hydra V3 is same as V1, but without antenna switch. 3cm RX input and 3cm TX output is
available on the SMA connectors. There is no TX amplifier. PCBs available on request.
See detailed description below.

Hydra V4:

Hydra V4 is shipped now. Better pin-diode switch on PCB, spec. to 13Ghz. TX amplifier
with NLB-310, see detailed description below. Output is 10mW.
Line-of-sight is no longer a requirement.

Frequently Asked Questions - FAQ

(please send mail for the Q&A, all answers will be available here.)

What is the price including shipping?

Hydra V2: € 99.-
Hydra V4: € 129.-
Tracked shipping is € 15.- to EU/UK, to US/VK/JA is € 20.-
Other countries € 20.- or € 25.-
Paypal is preferred. All prices are in EUR and include 20% VAT and are valid
only for orders in Nov.

How can I order?

Please send email (address see below) to me, including your shipping address. I will
contact you once i am ready to send the PCBs out.

What software do you use in general for Pluto?

Currently I do only the hardware, but my friends use SDRAngel, SDR-Console,
GNU-Radio and the Langstone project software. Once I have tried every possibility
myself in software, I will report here.
For now it seems that the Langstone software, with Raspberry Pi4 and 7" display is the
best for QSOs, but for testing purposes other solutions may be preferred.


-Amateur radio
-Portable testing equipment
-Microwave portable equipment

Other Published Articles:

Information about the El Cuatro FM/CW Microwave Multiband Handheld Transceiver, published
in DUBUS 3/2018 is here

Updates to the Hydra Article, published in DUBUS 3/2020:

The following clarifications to the schematic are found:
- on the +5V TX Line, the 100pF Capacitor should be very close to XX1002.
- both +5V TX and +5V RX line need a 2k2 or 3k3 resistor to ground to ensure switching
voltages at the specified range, for "low" 0-0,2V is specified.

Hydra V1 description:

is a extension for the ADALM-PLUTO (tm by Analog Devices) learning Module, and enables
the use of the 10Ghz Band (10368-10370, 10400-10450) and beyond. From a former project
"Hydra V0" was reused. For a detailed description, PCB layout and schematic see
DUBUS 3/2020.
X-Band (10Ghz) frontend for PlutoSDR

Pluto must be set to (e.g.) 5184Mhz for TX and receiver must be set to (e.g.) 618Mhz.
Any more questions? Please email me and the answers will be added to the FAQ.

Typical Hydra package contents

Hydra V1 package contents
All versions of Hydra areis shipped in an antistatic bag, with one SMA plug not
mounted, this has to be fittet to your Adalm Pluto, as the distance between the SMA
connectors is slightly different. The cable on the top is for +5V, a manual switch is
sometimes mounted for testing, but can be replaced by a relay (which is switched from
USB or Raspberry PI port). The board is tested for TX and RX performance, RX/TX
function and that the 25Mhz oscillator is continuously running. The TCXO for RX
is always on, regardless of RX/TX state to have more stable frequency.

Hydra V2 description:

Hydra V2: (blue) One additional amplifier stage was added to get more TX power.
new: Hydra V2
This is the first manually assembled Hydra V2 board. Very small parts, the smallest
IC is 1.5x1.5mm. The good news, I get used to assemble the board under the stereo
microscope in 5-10x magnification. More informations soon.

Description of Hydra V3, the headless Hydra.

Hydra V3 is without the antenna switch, there is a seperate SMA connector for TX
and a seperate connector for RX. You can add PA, LNA, filters and antenna relais
yourself as needed.
new: Hydra V3

If you are serious about activity on 3cm, please consider using a transverter.

Description of Hydra V4, the Power-Hydra.

Hydra V4 uses a different pin-diode-switch (ADRF5019) so there are less losses on
TX and RX. Also the spacing between the parts has improved for easier rework.
V4 is smaller (36x48mm) but has no longer the footprint for the EMI-shield.
The PA is a NLB-310 amplifier, and provides 10mW of output power.
10mW is enough for *any* line-of-sight QSO with a 40 or 60cm dish, and works even
with a mountain as reflector (27km total path length).
And - finally a new feature: The +5V RX can be switched on also during TX, or can
be active all the time. The switch voltage is derived only from the +5V TX line, so
you can find and hear your own TX frequency in GNU-Radio.

new: Hydra V4 10Ghz Extension

Bonus material, which was not available
in time for DUBUS 3/2020

RX/TX switching:

is always done with the same footprint for +5V TX and +5V RX.
It can be done manually:
- with a miniature switch (e.g. Hartmann SX254)
- With a small SPDT switch (see photo)
Hhttps://www.youtube.com/watch?v=9869CcKULwoydra X-Band RX/TX switching
or automatic from your Raspberry, laptop or PC:
- With a mechanical SPDT relay, which can be a seperate USB relay
- or a relay driven from Raspberry Pi 3.3V Pin (like Langstone project).
- The relay then provides +5V RX and +5V TX seperately to the pads, see above.
So no extra +5V supply to the Hydra PCB and no manual switch is needed.

LNB LO Options:

The LNB in default configuration works with 9750 Mhz (25Mhz x 390). The LNB
features also a "high band", where the multiplicator is 424 which gives 10600 Mhz
LO (25Mhz x 424). You can remove the 25 Mhz Oszillator and feed your own frequency
as a reference frequency. I successfully used 24,1 to 25 Mhz, but 26 Mhz failed.
So you could adjust the receiving frequency also to 144 or 432 Mhz, if you want.
So for synchronous receiving with several RCVRs you only have to feed the LNBs with
the same phase of reference signal.
Hydra X-Band frontend LO mod

About the author:

Fred, OE8FNK, now also microwave manager in OE, is doing UHF/SHF amateur radio for a
lifetime. His background is microprocessors and software, but interest radio and radio
astronomy made him build electronics and RF. All equipment is made to enable
all radio amateurs to participate in UHF/SHF activities, and to create local
activity on microwaves bands (70cm-3cm)
, often within the local club or district.
This is often done with the absolute minimalistic equipment, and the least
possible TX output power, but encourages some to maintain their equipment and activity
on microwave bands.
We are making contacts over a distance of 60-100km monthly in activity contest,
with 0.0003 to 0.06 Watts now for many years on frequencies from 1-10Ghz. And now even
doing experiments on 24Ghz and 122Ghz over shorter distances. Results are
documented and available at http://mikrowelle.oevsv.at

Still reading? Any more questions? Appreciate your comments and feedback :-)


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