Surecom SF 401 Plus

[Brian Reay]

I'm always on the look out for small, compact, test kit which I can
carry when travelling (I like to do some 'tinkering' on our longer
motorhome trips).

My latest (Ebay) buy is a Surecom SF 401 Plus, all of about £35.
(I had ordered one for less from China/Hong Kong be it never arrived and
I received a refund- I reordered one from France which arrived in a few
days.)

The beast is a combined Frequency Counter and CTCSS / DCS 'detector'. It
is about the size of a pack of 20 cigarettes. Internal (rechargeable)
battery - charger and cable supplied, are are two antenna.

It is supposed to cover 27-3000MHz, although it is only guaranteed or
100-3000MHz (?). The CTCSS/DCS detector only covers around 135-174 and
(about) 70cm (+/-) - not sure why that is so, it is simply stated in the
spec.

I've checked it against my GPS locked counter and accuracy at 2m and
70cm is within +/- 50Hz. (ie one digit in 4 dp). You can 'tweak' the
accuracy from the 'keyboard', if needed.

The only 'niggle', it defaults to 3dp and, while you can set it to 4dp,
it reverts to 3dp after being powered down.

Connector is BNC so, with an simple attenuator, you could us it as a
basic counter with a direct input.

[J1MBO ...]

"Brian Reay" <no...@m.com> wrote in message
news:og4353$iuh$1...@dont-email.me...

will it read out the frequency of digital signals that don't read out on a
normal frequency counter ? ......

[David Taylor]

On 24/05/2017 14:54, Brian Reay wrote:
> I'm always on the look out for small, compact, test kit which I can
> carry when travelling (I like to do some 'tinkering' on our longer
> motorhome trips).
>

> My latest (Ebay) buy is a Surecom SF 401 Plus, all of about £35.

> (I had ordered one for less from China/Hong Kong be it never arrived and
> I received a refund- I reordered one from France which arrived in a few
> days.)
>
> The beast is a combined Frequency Counter and CTCSS / DCS 'detector'. It
> is about the size of a pack of 20 cigarettes. Internal (rechargeable)
> battery - charger and cable supplied, are are two antenna.
>
> It is supposed to cover 27-3000MHz, although it is only guaranteed or
> 100-3000MHz (?). The CTCSS/DCS detector only covers around 135-174 and
> (about) 70cm (+/-) - not sure why that is so, it is simply stated in the
> spec.
>
> I've checked it against my GPS locked counter and accuracy at 2m and
> 70cm is within +/- 50Hz. (ie one digit in 4 dp). You can 'tweak' the
> accuracy from the 'keyboard', if needed.
>
> The only 'niggle', it defaults to 3dp and, while you can set it to 4dp,
> it reverts to 3dp after being powered down.
>
> Connector is BNC so, with an simple attenuator, you could us it as a
> basic counter with a direct input.

Looks interesting, Brian! I see it's on Amazon as well, albeit at a few
more pounds. Makes returning much easier, if that's needed. Having the
rechargeable batteries rather than PP9 (which another had) could be a
bonus too.

Something which measured FM deviation as well would be even more useful,
but, perhaps not surprisingly, I see nothing in a similar price range.

--
Cheers,
David
Web: http://www.satsignal.eu

[Brian Reay]

Yes, it has a 'digital' mode, that is another reason I bought it- so I
can check DMR radios.

[J1MBO ...]

"Brian Reay" <no...@m.com> wrote in message

news:og4dom$prk$1...@dont-email.me...

do you think it would pick up low power digital items like car key fobs?
......

[David Taylor]

On 24/05/2017 14:54, Brian Reay wrote:

> I'm always on the look out for small, compact, test kit which I can
> carry when travelling (I like to do some 'tinkering' on our longer
> motorhome trips).
>

> My latest (Ebay) buy is a Surecom SF 401 Plus, all of about £35.

> (I had ordered one for less from China/Hong Kong be it never arrived and
> I received a refund- I reordered one from France which arrived in a few
> days.)

[]> The only 'niggle', it defaults to 3dp and, while you can set it to 4dp,

> it reverts to 3dp after being powered down.

[]

If you press F4 (save) the 4-digit display is retained. Mine showed
799.9994 MHz uncorrected on an 800 MHz GPS-locked source, so I set the
correction to +3 and it now shows 799.9999 or 800.0000 MHz. As you
commented, being able to directly connect to the BNC input is rather
convenient.

GPS source:

http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=234

Only niggle with Amazon (or rather, their supplier) is that the unit I
got had no screen protector and had some slight scratches on the screen.
I'm waiting to see whether Amazon will just discount it a little as
I'm happy to keep a working item, rather than having the hassle of
return and re-order.

[J1MBO ...]

"Brian Reay" <no...@m.com> wrote in message
news:og4353$iuh$1...@dont-email.me...
>

how times change...I remember when you couldn't get an inexpensive Fx
counter that worked above 30 Mc/s now things are the other way around with
this unit .....

[J1MBO ...]

"J1MBO ..." <kinvig...@ntlworld.com> wrote in message
news:og4eir$spm$1...@dont-email.me...

does any one else knowif it it will? .......

[Brian Reay]

I've just tried it with the ones I have to hand and it doesn't, even
with them very close.

It would only give you the carrier frequency which is, I believe,
common, and published (I think 433.92MHz for the modern ones, the older
ones were around 418MHz- ignoring the IR ones of course).

You can hear them on a receiver- when I had a problem with one I used my
IC-R7100 to listen for the signal.

[Brian Reay]

On 27/05/17 07:44, David Taylor wrote:
> On 24/05/2017 14:54, Brian Reay wrote:
>> I'm always on the look out for small, compact, test kit which I can
>> carry when travelling (I like to do some 'tinkering' on our longer
>> motorhome trips).
>>
>> My latest (Ebay) buy is a Surecom SF 401 Plus, all of about £35.
>> (I had ordered one for less from China/Hong Kong be it never arrived and
>> I received a refund- I reordered one from France which arrived in a few
>> days.)
> []> The only 'niggle', it defaults to 3dp and, while you can set it to 4dp,
>> it reverts to 3dp after being powered down.
> []
>
> If you press F4 (save) the 4-digit display is retained.

Well spotted, thank you.

Mine showed
> 799.9994 MHz uncorrected on an 800 MHz GPS-locked source, so I set the
> correction to +3 and it now shows 799.9999 or 800.0000 MHz. As you
> commented, being able to directly connect to the BNC input is rather
> convenient.
>
> GPS source:
>
> http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=234

I built a GPS reference based on a Jupiter GPS module. Very useful.

>
> Only niggle with Amazon (or rather, their supplier) is that the unit I
> got had no screen protector and had some slight scratches on the screen.
> I'm waiting to see whether Amazon will just discount it a little as
> I'm happy to keep a working item, rather than having the hassle of
> return and re-order.
>

A bit of Duraglit or toothpaste + cotton wool will probably polish them out.

[J1MBO ...]

"Brian Reay" <no...@m.com> wrote in message

news:ogbp0q$222$1...@dont-email.me...

oh well the mustang is supposed to be on 315Mc/s got a load of cheap chinese
ones I want to test .....think they are dual band 433/315Mc/s......thanks

[Brian Reay]

On 27/05/17 17:02, J1MBO ... wrote:
> "Brian Reay" <no...@m.com> wrote in message
> news:ogbp0q$222$1...@dont-email.me...
>> On 24/05/17 18:10, J1MBO ... wrote:
>>> "Brian Reay" <no...@m.com> wrote in message
>>> news:og4dom$prk$1...@dont-email.me...
>>>> On 24/05/17 15:49, J1MBO ... wrote:
>>>>> "Brian Reay" <no...@m.com> wrote in message
>>>>> news:og4353$iuh$1...@dont-email.me...
>>>>>>
>>>>>> I'm always on the look out for small, compact, test kit which I can
>>>>>> carry when travelling (I like to do some 'tinkering' on our longer
>>>>>> motorhome trips).
>>>>>>

>>>>>> My latest (Ebay) buy is a Surecom SF 401 Plus, all of about £35.

Are you sure about the 315MHz? I've never heard of that frequency being
used for key fobs. The older ones were, I thought, on 418Mhz until they
standardised on 433.92MHz.

I had one of those remote controls that have IR transmitter you place
by, say, the VCR and the remote has a transmitter in it. It was on
418MHz but the tx 'died'. I got a replacement tx unit and receiver
module (long story) and swapped them over - they were on 433.92. The Tx
module was just like a transistor- about the size of an AF117. The
receiver was the whole lump so I didn't look inside.

You can, or could, buy the tx modules quite easily and I assume the rx
modules were also available. They are pretuned so you don't need to
fiddle with them, just solder into place. The tx module was only a
couple of quid but I used one from a car alarm key fob- see below.

I also replaced one in a car alarm in one of our old cars- I couldn't
get a replacement fob. I spoke to a localish car alarm company and they
gave me a hand full of old fobs. I looked in them until I found a
suitable part and used it. There was another one I used in the remote
control above.

If your counter won't detect the frequency then try a scanner- they are
more sensitive. I don't think the receivers are that selective. I looked
into the some of the receivers in the past and they are very simple and
the frequency can be a bit 'off' on tx and the rx will still accept it.
It is the code that matters. Some of the simple ones set the code by
solder links- the one on the old fob I mentioned did. It was some time
back- the alarm was fitted in 1991 or so.

[mm0fmf]

315MHz is used for American key-fobs but is not licensable for that
purpose in the UK.

[Brian Howie]

On Sat, 27 May 2017 17:02:38 +0100, "J1MBO ..."
<kinvig...@ntlworld.com> wrote:


>oh well the mustang is supposed to be on 315Mc/s got a load of cheap chinese
>ones I want to test .....think they are dual band 433/315Mc/s......thanks
>

I use a cheap RTL Dongle and HDSDR free software for this sort of
stuff and wide-band VHF/UHF general coverage rx; they do about 24MHz
to 1766MHz. They've no problems detecting the 433MHz keyfobs and
will cover 315MHz and the amateur bands from 24MHz to 1296MHz.

You can get them from Bangood.com

<https://www.banggood.com/USB2_0-Digital-DVB-T-TV-Tuner-Recorder-Receiver-Stick-RTL-SDR+DAB+FM-p-84565.html?rmmds=search>

or there are alternatives at :-

http://www.essexham.co.uk/realtek-sdr-dongle

Some of the more expensive ones are more stable in frequency.

The HDSDR software here:-

http://www.hdsdr.de/

You have to download the dll file for the RTL dongle

There's also software available to turn the dongle into a wider band
spectrum analyser.

For example :-

https://github.com/pavels/spektrum

I've got them to work on a fairly low spec laptop.


Brian

[Brian Reay]

Out of interest Brian, have you looked into modifying any of the
'dongles' yourself for improved frequency stability?

As I understand it, it is a fairly simple mod, just a part swap (albeit
it a surface mount but probably do-able with a heat gun). The cost of
the modified ones seems disproportionately high and a bit of tinkering
is always fun. If it goes bad, it isn't the end of the world.

[Brian Reay]

On 29/05/17 17:02, mm0fmf wrote:


> 315MHz is used for American key-fobs but is not licensable for that
> purpose in the UK.
>

Ok, I've learned something. I'm not sure what 315MHz is allocated to
here- I have an OFCOM list somewhere. I doubt they would be too
bothered, there must be 100s of American cars in the UK with fobs on
that frequency but the chances of them causing a problem must be
minimal. The potential problem is the kind of thing Jim has mentioned
when a local tx causes the fob to stop working, which people have seen
with the ones on 433.92 when an amateur tx is operating- there have been
a number of cases of that.

I stumbled on a case in the US on YouTube recently where one of those
anti-shoplifting loop things by shop doors had a fault and 'blocked' key
fobs in the car park (sorry parking lot). The local amateur radio club
stepped in an traced it and reported it to the FCC. Presumably it was
emitting a spurious output on or near 315MHz. As I mentioned previously,
the receivers aren't very selective- I don't think they are even
superhets- they may even be super-regens. I think the transmitters are AM.

When we bought this house it had a remote garage door opener. I'm pretty
sure it was a US design. I forget what frequency it was on but it was
certainly AM. It was 'coded' but would sometimes open if I ran about 50W
on 2m, even though it certainly wasn't VHF or UHF. A couple of ferrite
rings cured it. We've long since replaced it and the garage door!

[David Taylor]

On 30/05/2017 11:36, Brian Reay wrote:
[]> Out of interest Brian, have you looked into modifying any of the

> 'dongles' yourself for improved frequency stability?
>
> As I understand it, it is a fairly simple mod, just a part swap (albeit
> it a surface mount but probably do-able with a heat gun). The cost of
> the modified ones seems disproportionately high and a bit of tinkering
> is always fun. If it goes bad, it isn't the end of the world.

One of the better ones at a reasonable price and UK stock is:


https://shop.technofix.uk/super-stable-1ppm-tcxo-r820t2-tuner-rtl2832u-rtl-sdr-usb-stick-version-3

[Brian Howie]

On Tue, 30 May 2017 11:36:43 +0100, Brian Reay <no...@m.com> wrote:

>On 29/05/17 19:45, Brian Howie wrote:
>> On Sat, 27 May 2017 17:02:38 +0100, "J1MBO ..."
>> <kinvig.

>Out of interest Brian, have you looked into modifying any of the
>'dongles' yourself for improved frequency stability?
>
>As I understand it, it is a fairly simple mod, just a part swap (albeit
>it a surface mount but probably do-able with a heat gun). The cost of
>the modified ones seems disproportionately high and a bit of tinkering
>is always fun. If it goes bad, it isn't the end of the world.
>

I've never tried it . The ones I have here have a 28.8MHz thru-hole
xtal. Two pins so it's easy to remove.

The mod I've seen is to replace it with something like this.

https://www.amazon.co.uk/gp/offer-listing/B0177YS1CA/ref=dp_olp_0?ie=UTF8&condition=all


I've also a funcube dongle, which has better stabiility, but these
cost considerably more.

Brian

[Brian Reay]

On 30/05/17 15:31, Brian Howie wrote:
> On Tue, 30 May 2017 11:36:43 +0100, Brian Reay <no...@m.com> wrote:
>
>> On 29/05/17 19:45, Brian Howie wrote:
>>> On Sat, 27 May 2017 17:02:38 +0100, "J1MBO ..."
>>> <kinvig.
>
>> Out of interest Brian, have you looked into modifying any of the
>> 'dongles' yourself for improved frequency stability?
>>
>> As I understand it, it is a fairly simple mod, just a part swap (albeit
>> it a surface mount but probably do-able with a heat gun). The cost of
>> the modified ones seems disproportionately high and a bit of tinkering
>> is always fun. If it goes bad, it isn't the end of the world.
>>
>
>
>
> I've never tried it . The ones I have here have a 28.8MHz thru-hole
> xtal. Two pins so it's easy to remove.
>
> The mod I've seen is to replace it with something like this.
>
> https://www.amazon.co.uk/gp/offer-listing/B0177YS1CA/ref=dp_olp_0?ie=UTF8&condition=all
>

Even easier than I thought, I assumed they used one of those SMD devices
with a built in oscillator. I will have to crack mine open and have a look.

Chances are you can get a stable oscillator off Ebay for a good price.
The other option is to knock up something locked to a GPS source. I keep
thinking I should make more use of my GPS locked source- the idea of
having a central reference I can lock several things too quite appeals.

>
> I've also a funcube dongle, which has better stabiility, but these
> cost considerably more.

The Funcube is in a different league but, as you say, much more
expensive. I have one of the early ones- probably the 'Mk2' in
unofficial terms. It is remarkable the way Howard (G6LVB) built the
first prototypes 'on his kitchen table' so to speak.

I can't say I'm a fan of 'dongle radios', I'm more of a traditionalist.
I like a proper box with proper controls. I tend to use dongle radios
more as test equipment / test aids. Even my PCR1000 is used as a simple
spectrum analyser more than a radio. I should really invest in a real
spectrum analyser...

[Brian Reay]

Thank you David, that is certainly a better price than some I've seen
for the 'modified' ones. However, I'm tempted to consider modifying one-
I'm more of a tinkerer than a user of SDRs so the fun is in doing the
mod. I will add it to my list of things to 'get round to'.

Currently I'm playing with my new toy- the Selective Level Meter. I need
to get a decent antenna up for (V)LF. 'Senior Management' caught me
planning a new large loop but, as it involved some ladder work, she said
'no'- she hates me going up ladders. I'll have to wait until she has a
day shopping with one of the daughters ;-)

[David Taylor]

On 30/05/2017 16:23, Brian Reay wrote:
[]

> Thank you David, that is certainly a better price than some I've seen
> for the 'modified' ones. However, I'm tempted to consider modifying one-
> I'm more of a tinkerer than a user of SDRs so the fun is in doing the
> mod. I will add it to my list of things to 'get round to'.
>
> Currently I'm playing with my new toy- the Selective Level Meter. I need
> to get a decent antenna up for (V)LF. 'Senior Management' caught me
> planning a new large loop but, as it involved some ladder work, she said
> 'no'- she hates me going up ladders. I'll have to wait until she has a
> day shopping with one of the daughters ;-)

I still tinker but it's more with Raspberry Pi cards and GPS receivers
these days. Have built some RF stuff, though, and enjoy using the RTL
dongles, SDRplay (can't stand the software), and Airspy. Useful devices
for measuring the (IF) spectrum from 10 GHz satellite transponders. I
must confess that Amateur Radio is handled by Japanese and Chinese
devices these days, and my 1970s 2m AM and 432 MHz TV gear is gathering
dust.

VLF is interesting, but I don't have a decent antenna so it's very noisy
here. Appreciate the ladder problem, but the last time I stretched up
to change a light bulb resulted in a hernia eventually needing an
operation! That's when I bought the FT-817ND, and now the Wouxun
KG-UV9D which I've had fun programming.

[mm0fmf]

I doubt there will be much of a problem in reality. But that doesn't
make them any less illegal when used in the UK however.

[Paul Cummins]

In article <9hpoic1hqpjdb2d2f...@4ax.com>,

Br...@nospam.demon.co.uk (Brian Howie) wrote:

> I use a cheap RTL Dongle and HDSDR free software for this sort of
> stuff and wide-band VHF/UHF general coverage rx; they do about 24MHz
> to 1766MHz.

I've just picked one of these up - surprisingly sensitive, even plugged
into the back of a PC.

They also show me exactly how dirty the signal out of my Baofeng UV5R is!

Usefully, there is software available to do pretty much everything with
the signal, including well.io for DAB/DAB+ Dream for DRM, various DTV
beasties and the AirSpy and SDRSharp software for pretty much anything
audible by way of carrier.

Hooked up to a CR9800 antenna, its interesting to see the peaks and nulls
involved in making 28. 50, 144 and 430 work off the same piece of metal.
It's great for DAB, less good for Broadcast FM. 446 is within bandwidth
for listening to the toy radios, and the two CB bands are also within the
3:1 range of the 10m segment.

I think I'm getting somewhat more than the traditional 1/4 mile reception
on those bands too.

No doubt if I had a wider band scanning aerial, or something higher up
the building, I'd hear much more, nonetheless, for something that cost
less than £15 delivered, I'm not arguing.

--
Paul Cummins - Always a NetHead
Wasting Bandwidth since 1981

[Jeefaw K. Effkay]

I was playing with a spectrum analyser at "the Mothership" in Reston last year, and was surprised to find that the keyfob for my rented Chevy Cruze was in fact on 433.92MHz.

A colleague's redneck-mobile keyfob was on 315MHz.