Some basic questions on the HF+
Paul Gulliver <paulg1953@...>
Hi, I'm new to this group and have some rather basic questions.
I'm considering buying a Airspy HF+ for use in receiving HFDL messages, this involves monitoring several frequencies at once. Is there any sensible limit (say up to 10) to the number of frequencies that can monitored at once using something like SDR Console. Also is there a limit to the frequency range that can be monitored at the same time, I believe HFDL can be between around 3MHz and up to 22MHz.
Does anyone else here us HF+ for this purpose, if so any recommendations or advice.
On 11/11/2018 11:17 AM, Paul Gulliver wrote:
Hi, I'm new to this group and have some rather basic questions.The HF+ has a maximum "bandwidth" of 768KHz. Decide accordingly.
On Sun, Nov 11, 2018 at 08:51 PM, Paul Gulliver wrote:
Hi, I'm new to this group and have some rather basic questions.HF is a very different ball game, and the common amateur knowledge built around wide band SDRs during the last few years do not always apply.
For example, with strong nearby broadcast signals, you must reduce the gain of "TV Tuner" based receivers to avoid saturating the different stages. Incidently, this also results in weak signals like HFDL to sink into the noise.
A lot of professional customers already use the HF+ for monitoring HF telemetry signals in similar conditions, and they use as many receivers as needed to cover the required bands. This ensures acceptable performance compared to high end dedicated receivers while costing a fraction of the price.
There is also an upcoming review that shows how the HF+ with basic filtering compares to things like Racal RA3791.
We are very far from the era of TV Tuners branded as HF receivers :-)
On 20181118 04:16:05, prog wrote:
On Sun, Nov 11, 2018 at 08:51 PM, Paul Gulliver wrote:Am I correct that you are saying an input filter helps interference (of course) so monitoring several widely separated weak signals won't work and even monitoring more than one frequency within the input filter's bandwidth won't work?
Suppose say roughly 2.4 MHz is desired. You install a 240 kHz filter in front of AirSpy HF+. You try to listen to 2.403 kHz and 2.447kHz at the same time with something like SDRConsole that it will not work? That sounds like nonsense. (And, of course, 2.565 MHz would not work at all well as the Nth simultaneous frequency due to the front end filter.)
Hi Paul,toggle quoted messageShow quoted text
a good rule is to not pay for more dynamic range than
you need. Maybe you can borrow a spectrum analyzer
somewhere to get an idea about what strong signals you
An alternative would be to buy an rtlsdr plus a ham it up
to use as a poor mans spectrum analyzer. This would give
2 MHz chunks of spectrum, but I think you can find software
that would sweep that 2 MHz chunk over the 0 to 30 MHz range.
Once you know where the strongest signals are - and how
strong they are - you could take a rational decision.
The Airspy R2 with an up-converter would give 9 MHz chunks
of alias-free spectrum. Two such systems would cover
3 to 21 MHz. If you would tolerate modest alias spurs you
would cover 3 to 22 MHz.
A high-pass filter that would remove AM broadcast and
maybe a low pass filter to get rid of FM broadcast - and
for your purpose, to get rid of everything above 22 MHz,
might give a situation where the R2 is fully adequate.
In case there are some problematic frequencies - maybe
you have a local radio amateur - you could add notch
filters to attenuate certain narrow frequency ranges.
(When you have a wideband SDR it is easy to tune notch
In case you want to listen for HFDL close to very strong
signals you might need the HF+.but it would give only
a 0.66 MHz chunk of RF spectrum. To cover 3 to 22 MHz you
would need 29 of them.
I think a pair of R2 + Spyverter with maybe some notch filters
would serve you well. Should you want to listen to a frequency
that is to much attenuated by a notch you could get a HF+
and use it on that particular frequency range - connected before
On Sun, Nov 11, 2018 at 08:51 PM, Paul Gulliver wrote:HF is a very different ball game, and the common amateur knowledge built around wide band SDRs during the last few years do not always apply.
On Sun, Nov 11, 2018 at 8:51 PM Paul Gulliver <paulg1953@...> wrote:
Also is there a limit to the frequency range that can be monitored at the same time, I believe HFDL can be between around 3MHz and up to 22MHz.
It's not that HFDL can appear anywhere between 3 and 22 MHz. HFDL channels are grouped in subbands, like this:
So with Airspy HF+ you could monitor all channels from any subband at once, but only one subband at a time.
Obviously it doesn't make a lot of sense to monitor all subbands simultaneously (read: daily propagation cycle).
hello leiftoggle quoted messageShow quoted text
there are seferal scanning software avaiable for the rtl sticks
one that i often use is from touchstone
that soft is normally made for the rf explorer but can be used for an rtl stick too!!
and yes ... it takes the 2 megs chunks and stitches them together
if needed you can scan several hundred megs at once
or ... with an upconverter scan 100-130 meg (guessing converter has 100 megs clock)
and you have a scan over complete shortwave 0-30
not an exact replace for a real wideband sdr ... but for a chap mans analyzer it is usable
i just had some fun on the weekend with my brandnew pluto sdr
made some tx tests on 70cm and ... with just that tiny ten milliwatts i coild reach our repeater in 40km distance
superb sdr setup that pluto :-)
Am 19.11.2018 um 00:44 schrieb Leif Asbrink: