Re: VLF: getting on 8.970kHz

[JACK ASKEW <va7jx@shaw.ca>]

Jacek,

Thanks for that helpful information on the neo-7m modules.

Jack

---

From: "Jacek Lipkowski" <sq5bpf@lipkowski.org>
To: "rsgb lf group" <rsgb_lf_group@blacksheep.org>
Sent: Friday, September 8, 2017 12:49:58 PM
Subject: Re: VLF: getting on 8.970kHz

look for ublox neo-7m modules. they will go over 10MHz (neo-6m modules
will generate <1kHz). they were avaliable on dx.com, ebay.com and other
auction sites. these will work <10MHz (according to manufacturer specs,
they will go higher). they can be used for generating a signal directly
(it's an NCO with 48MHz reference, so try to use frequencies
48MHz/(integer value) for best spectrum purity), or as a reference for
ebsynth

the neo-7m modules are very cheap (abt 10 euro). then only problem with
them is that they don't have a tcxo (blowing compressed air at them will
cause them to loose sync)

jacek


On Fri, 8 Sep 2017, JACK ASKEW wrote:

> Date: Fri, 8 Sep 2017 11:17:05 -0600 (MDT)
> From: JACK ASKEW <va7jx@shaw.ca>
> Reply-To: rsgb_lf_group@blacksheep.org
> To: rsgb lf group <rsgb_lf_group@blacksheep.org>
> Subject: Re: VLF: getting on 8.970kHz
>
> Hi Stefan
>
> It appears that Amazon will not ship that XCSourse GPS Locating Module NEO-6M to Canada. 
> I questioned XCSource why this is so and I'm waiting back for an alternate or answer from
> them.  There might be another choice out there that does but have not come across it as
> yet.
>
> 73, Jack - VA7JX
>
> __________________________________________________________________________________________
> From: "DK7FC" <selberdenken@posteo.de>
> To: "rsgb lf group" <rsgb_lf_group@blacksheep.org>
> Sent: Thursday, September 7, 2017 1:40:49 AM
> Subject: Re: VLF: getting on 8.970kHz
>
> Hi Jack,
>
> Ok, so i'm continuing to write on the reflector. It is not at all a waste of time to read
> the conversation. Most potential newcomers are in a similar situation like you and they
> may be interested to see that there are more stations considering to get on the air down
> there, world wide! For example, IK1HSS tried to receive my VLF carrier transmission, but
> no one knows, except me. Sharing thoughts can never be a waste of time. Don't we all have
> loads of time available anyway? As long as someone own a TV, there must be more time than
> needed :-)...
>
> Now, forget the loop for VLF transmissions. Your inv-L will give a very good radiator for
> VLF! Important parameters are height and capacity, you know. In the first steps you don't
> need QRO. 100 W from a normal audio PA is sufficient because the voltages will be very
> high! At 250 W on 8270 Hz i'm getting about 30 kV across the wire. Your wire and the
> isolators have to withstand that voltage. If the wire is to small, there will be partial
> discharges. It makes no sense to run 1 kW then. It would rather make sense to use a bigger
> wire or even more wire (capacity).... The first thing to concentrate on is a stable signal
> generator using 1 PPS.
> Buy that one for example:https://www.amazon.com/XCSOURCE-Locating-Aircraft-Controller-TE624/dp/B01N2GK1YK/ref=sr_1
> _6?ie=UTF8&qid=1504772304&sr=8-6&keywords=neo-6m
>
> You seem to have a high antenna capacity which is a big advantage. It is very promising
> that you can radiate a very strong signal. There is no time to loose!
> For the coil i suggest to use a single layer coil using 0.4 mm or even 0.6 mm diameter
> wire on a tube with 0.3 m diameter or higher. It depends on the space you have for placing
> the coil. It should stay dry all the time!
> You need patience to wind it but it is very relaxing. :-)
>
> I recommend to build an analog amperemeter covering 0...1 A antenna current. It is trivial
> to build it. Just use a bridge rectifier out of fast switching diodes such as UF5404 and
> connect the meter to the DC side. The AC side is connected between coil and ground.
> The coil is for compensating the capacitive component of the wire. The residual resistive
> component is transformed to the PA output impedance using a big ferrite transformer
> (toroid) which also provides galvanic decoupling.
>
> Now, just order the GPS module, the wire and search for a suitable coil body :-)
>
> 73, Stefan
>
> PS: With that antenna, you can become the strongest amateur VLF station!
>
>
> Am 06.09.2017 17:12, schrieb JACK ASKEW:
>       Hi Stefan
>
> Thanks for the reply.  Sorry to hear that my ERP will be so little with this setup. 
> A few 10dBs is a lot, I had no idea it would be that much.  I just assumed I could
> make up the difference by running a much larger audio amplifier.  It would no be
> hard to put 1KW amplifier on with the availability of some cheap 12V car amps now
> available.  But maybe this might not be enough power.
>
> For MF I'm currently using a inverted L ~73m long, 24m of that has 3 wires as a top
> hat, but hopefully will be increasing that soon.  The height of the antenna is ~24m
> at one end and >36m at the farthest end.  The Tx is a HB set up with 4 FETs running
> class D, capable of 1KW but I have not pushed it that far as yet.   I have been
> limiting it to ~300W for local contacts between here and stations South of the
> Island.  I use an Icom R75 receiver for receiving, it seems to work very well on MF.
> Best heard DX so far on WSPR is ZL2BCG and VK4YB.
>
> I was hoping you would say that QRSS240 would work with this limited budget set up.
> It doesn't sound like I need to proceed much further unless I can find a much larger
> audio power amplifier, a lot of patience, a lot of luck and a good GPS receiver.  I
> did look at a few of the NEO-6M GPS units, but not sure which one on Amazon you were
> referring to.
>
> I agree maybe I could go on the reflector with our conversations, however since
> using even moderate size loop on this dreamer's band does not look realistic,
> perhaps it would be a waste of everyone's time?
> I'll play with it for a few more days if things don't improve I'll pack it all up.
>
> Thanks for your help Stefan.
> 73, Jack - VA7JX
>
>
> __________________________________________________________________________________________
> From: "DK7FC" <selberdenken@posteo.de>
> To: "Jack Askew" <va7jx@shaw.ca>
> Sent: Tuesday, September 5, 2017 3:16:05 AM
> Subject: Re: getting on 8.970kHz
>
> Hi Jack,
>
> Can we do the conversation on the reflector maybe? There is little activity and each
> conversation may help to rise some inspiration to lead to an increased activity...
> Your decision, just reply to the reflector in the next answer if you like.
>
> Well, i understood the procedure you're describing and this is of course the way to
> go for getting a resonance on the desired frequency.
> But, the ERP will be so little with this setup, i guess you are a few 10 dB away
> from leaving a trace on VE7SLs site.
>
> Which antenna are you using for LF and MF? A typical top loaded vertical antenna
> will give you the best results on VLF as well. What is the capacity of that antenna,
> in pF?
> But i understand, a loop is much easier to match on that frequency, easier than
> winding a large coil :-) But if you want to cross 186 km, which is a serious
> distance already, you will need to large coil and several kV across the antenna!
> Furthermore you won't manage QRSS240 on that band. QRSS 240000 is more realistic!
> That means, you need a receiver and transmitter that has the necessary stability.
> The cheapest and best way to go is using a GPS module like NEO-6M, which is
> available from Amazon. It provides a PPS pulse which must be fed into the mic input
> of the soundcard. Together with SpecLab you can generate a perfectly stable tone
> then, as well as DFCW, QRSS, EbNaut, etc.... The same must be used on the RX site.
>
> It is also helpful to do local tests, maybe with a notebook, in
> 1...2...3...4...5...6 km distance, just to get an impression...
>
> What do you think?
>
> I would say you can build the system from junk box parts mostly, that the advantace
> to the activity on the other end of the spectrum :-)
>
> 73, Stefan
>
> Am 04.09.2017 22:42, schrieb JACK ASKEW:
>       Hi Stefan
>
> I'm having problems finding your right email, so if you get this twice I
> apologize. 
>
> I have been trying to get a signal on 8.970kHz but with little success.  Since
> I'm on a limited budget, I have decide to try a large coaxial loop instead of
> a large coil. I chose RG-59 coax (center and shield) since it has a low
> resistance as appose to copper wire. The bottom of the loop is only ~10m off
> the ground but the top side is ~21m up, circumference is ~76m. The mid point
> goes down to a matching box consisting of a pc board with HV caps and a
> FT-240-78 core with a sec and pri winding. The primary is 11T of of #14 ins
> wire and a secondary of #18 awg enamel wire with 55T which connects to a
> chassis mount SO239 for the coax which goes back to the Tx amp ~30m away.  The
> HV caps totaled 2.86uF and is in series with one side of the coax loop. The
> loop measured 100uH, so the combined capacitors plus the 100uH loop seemed to
> be close to the calculated values, but I think it could have been higher. The
> Tx is a simple 140W audio amp driven by a Windows free downloaded program
> called Audio Measuring Systems.  I measured 2A of RF using a calibrated RF
> ammeter. The same meter was used to select the capacitor values for maximum
> O/P.  I tried using a scopematch designed for .475 MHz but I guess the toroid
> across the internal coax line is too lossy as it gets warm and besides the
> current reading was very low compared to the voltage. 
> I don't know how far I can Tx yet.  Steve, VE7SL has tried to receive me, he
> is ~186 km and used a Perseus receiver with ~24Hz BW and QRSS 240 but no luck
> so far.
> We think we might have too low of a EIRP for that distance.
> Is there any other way of optimizing the RF O/P besides using a RF ammeter?
> Your thoughts on this would be much appreciated.
> Thanks in advance.
> 73,
> Jack Askew - VA7JX
>
>
>
>
>