Computer controllable antenna tuner

GNU Radio
1

Hi,

Does anyone know a good antenna tuner with a serial port, usb or
ethernet
connection that allows you to tell the tuner what frequency to tune to?
I
could really use something like this.

Also, does anyone know of a good commercially available magnetic loop
antenna for the HF band (1-20 MHz)? Again, I’d want to use a computer to
tune the antenna for a certain frequency range.

juha

2

Hi Juha,

there’s a lot of devices that do your job.
From the “classic commercial-grade” devices of the USRP line,
to cheaply available rx modules like the (in)famous dvb-t dongles. You
can use the tuners on old PCI tv cards and a ton of other stuff.
It all depends on what you need to do: What frequencies do you need to
tune to? What bandwidth do you need afterwards? Do you want I/Q or are
you basically doing AM? Want to have ADC afterwards or do you really
need the analog baseband?
For your “commercially available tunable magnetic loop antenna”: I don’t
know. Not my kind of technology. Try a random used car radio that can
receive MW broadcasts and does the tuning digitally. Most probably
you’ll find a tuner module that works well but has no available
documentation whatsoever. Use your favourite digital analyzer to find
out how the microcontroller interfaces with that. Or ask your RF IC
manufacturer of choice. They build hardware. GNU Radio has nothing to do
with that.
However, this question is awefully unspecific and has little to do with
GNU Radio, as it is a software radio system (and less concerned with the
hardware; anyway, 1-20MHz sounds a lot like baseband to me).

Greetings
Marcus

Am 11.05.2013 14:37, schrieb Juha V.:

3

On Mon, May 13, 2013 at 10:52 AM, Marcus M. <
[email protected]> wrote:

For your “commercially available tunable magnetic loop antenna”: I don’t

I believe he is looking for something more like an antenna coupler/tuner
used in HF applications to tune and impedance match for maximum power
transfer:

Antenna tuner - Wikipedia

As for not talking about hardware on the GNU Radio mailing list - I find
that a little silly. While GNU Radio is more about a framework for
processing baseband signals, there’s also the real need to interface to
the
outside world. Dynamic range, gain, and all the little hardware bits in
the radio front end are all valid discussion points and completely on
topic, in my opinion.

Brian

4

I’m talking about “antenna tuners”. This is a device that matches the
impedance of an antenna to a radio. An example of a device I’m looking
for
is the LDG AT-100PC. Unfortunately LDG doesn’t make them any more.

PS. 20 MHz isn’t that much bandwidth to handle in software nowadays.

juha

On Mon, May 13, 2013 at 10:52 AM, Marcus M. <

5

for processing baseband signals, there’s also the real need to
interface to the outside world. Dynamic range, gain, and all the
little hardware bits in the radio front end are all valid discussion
points and completely on topic, in my opinion.

Brian

I agree with Brian. If it’s radio related and kinda-sorta touches on
SDR, it’s a valid thing to discuss here.

A quick google yielded this:

There are probably others.

Also, some of the HF-only SDRs out there have a built-in switchable
filter bank.

Once you move beyond HF, it becomes increasingly difficult to decide
where to put your filter responses, which is why SDRs that are intended
for
“DC to light” use tend not to have much in the way of front-end
selectable filters – any choice the manufacturer makes would likely be
“wrong” in
as many cases as “right”. Any any filters in the front-end, before
the first gain stage, will contribute to an increase in noise figure.
So you have to
filter after the LNA stage to maintain noise figure, but you’re
still, then, in the tenuous situation of likely continuing to run into
analog non-linearity
problems with strong signals within the DC-light passband of the
first-stage LNA.

What we need is either:

 (A) Microwave filters that have impossibly-low insertion loss (made

from super-cooled unobtanium, likely)

or

(B) HEMT/GaAs/SiGe transistor technology that can offer insanely-low

noise figure at the same time as offering insanely-high linearity, like
OIP3 of +50dBm with small-signal gains of 25dB or better, and
1dB or better noise figures :slight_smile:

6

As for not talking about hardware on the GNU Radio mailing list - I find
that a little silly. While GNU Radio is more about a framework for
processing baseband signals, there’s also the real need to interface to
the outside world. Dynamic range, gain, and all the little hardware
bits in the radio front end are all valid discussion points and
completely on topic, in my opinion.

Brian
Hi Brian, Hi Juha,
I didn’t mean to stifle hardware discussions at all - it just stroke me
as a little bit odd to ask gr-discuss a question that, although being
technically related to software defined radio, asks for something that
is kind of like “an antenna tuner buying guide”; it’s only logical to
ask a question like “hey, I’d like to get medium wave audio broadcast
transmissions, what do you guys use for a tuner” here. It’s less logical
to ask “I’d like to buy a 1-20MHz tuner”, without adding a little more
specs than “computer controllable”.
Yes, we are software radio users. But we are not the right point to
start looking for an antenna tuner, impedance matcher etc. in my
opinion. That being said, I think Juha has asked a valid question, and
I’d totally like to see him use that antenna / tuner / system with GR,
and therefore I’d actually hope someone helps him choose a good
component.

Sorry that I came around arrogantly, I didn’t mean to.

Greetings
Marcus

7

Marcus there are some things you need to be aware of. First the
bandwidth
of a small magnetic loop, like your describing is really small

On Mon, May 13, 2013 at 11:20 AM, Marcus M. <

8

Sorry didn’t finish my email for hitting send.

Marcus there are some things you need to be aware of. First the
bandwidth
of a small magnetic loop, like your describing is really small (2-6 KHz)
for the frequency range that your describing. Assuming that is ok I
don’t
know of a commercial solution. You can use this calculator to get a
general
idea Small Transmitting Loop Antenna Calculator • 66pacific.com .I am
currently planning on building one of these loops for the 40-20 meter
bands
using heliax 1 5/8 inch for the outer loop and a vacuum variable for the
tuning capacitor controlled by either a arduino or rasp pi. I am still
working on my plans but if your intent on utilizing one of these
antennas I
suggest you check out the group at www.magloop.com. If you not planning
on
transmitting a PA0RDT may be better. It is smaller. It is an active
antenna
and does require power but the websdr guys are getting good results with
it. I would like to build one in the future as well. See google for more
references but it is suppose to work well from 10KHz to 30MHz.

73 Jeff N6SDR