500kHz

I subscribe to the RSGB -LF group emails as one day I might get a NoV for 500kHz. Part of the new antenna builds will be aimed at improving my antennas for this band.

Last xmas during the GQRP xmas contest I operated cross band (3.5MHz/500kHz) manual CW with several that do hold NoV on 500kHz. Operation on 500kHz is a very narrow band and I found my FT817 could be used without any modification what so ever to RX the signals so I connected it to my 6BTV vertical adding a base loading coil 'bucket load' (Literally a bucket and c200m of multistranded wire wrapped around the bucket). Adding the base coil made the signals jump maybe 1-2 S points. I parked the RX on 502kHz and listened a lot.... after a time I heard some of those I saw post on the reflector so I thought here goes nothing... and emailed one or two and asked if interested in x band operating.

Operation this way the first time you do it is odd as you RX on 500kHz but tx on 80m frequencies. Still once you get the hang of it, it is pretty easy. Having a rig that operates split helps a lot but you can do it manually with two rigs.

Anyway suffice to say I manged a dozen or so contacts even with my completely awful cw and even posted on GQRP list after working Ian G3ROO this way. The LF activity seems to have increased of late as the nights draw in again.

Note that the humble softrock RX can be employed on 500kHz and I have a dedicated RX built just this way.





I also built a clone of M0MBU TX starting from the design in RSGB LF Today using MOSFETS, This is a picture of the final board, so don't get into problems I have not added the MOSFETS to it so cannot be used for TX. You can see the holes for the TO220 heat sink screws in the middle of the board. The whole board will be bolted to a heatsink. I modified the design to use a DDS based VFO not a 4MHz resonator (didn't have one at the time) and a divider network. The VFO feed comes in to the two holes on the bottom right, with the 4427 IC (8 pin DIL) just above. The DDS VFO uses a free AD9851 but with DIL dip switches not a PIC and rotary controller (originally an idea from Hans Summers http://www.hanssummers.com/radio/dds/index.htm). There are many different designs out there for LF capable DDS. I created the TX PCB layout with Express PCB and blue press n peel film and then etched it. The track side shows the wide spacing of the different parts. More as an exercise if could it be done that should it be done I took this and a few other project boards to FDIM show and tell. Most of the components were salvaged from an old APC UPS which was a wonderful source for the high value capacitors needed. I even include an LPF on the board (left hand side the paired up capacitors) as I wanted to use this /P from a beach with a kite antenna.... maybe one day.

For the shack a PCB box containing a 7 pole LPF for 500kHz was also constructed complete with SO239 connectors the design came from http://www.g0mrf.freeserve.co.uk/lpf.htm I think, not checked log, that G0MRF was one of those xband QSO.


To obtain an NoV for 500kHz it is important that you show you can meansure the field strength of the antenna (this site is for LF generally http://www.strobbe.eu/on7yd/136ant/#ERP) so I also started to build a field strength meter following a design by Dick, PA0SE
http://www.wireless.org.uk/pa0se.htm using a cheap digital meter. I bought a box of 10 of them for £2 and I have employed a few about the shack, one as an RF probe another pair monitor the V and I of a HB power supply. I have a wide band FSM using an AD8307 as well so might see if I can add a band pass at the front as well.

Lastly you have to demonstrate that you can measure frequency and I have a PIC based frequency meter that I know will work down to 100kHz ready for use. I calibrated it against a 1Mhz crystal oscillator but I probably have to do better than this.

All of this was a while back now and I was not successful with my NoV application earlier this year for some reason, I didn't get a reply even, but then the 3B8 trip and other activities took over. I will reapply shortly and now the ERP level is 1W which is 10 times what it was at 100mW last year. I might try a qQRP station on 137KHz for fun, SPRAT 123 featured a 137kHz qQRP circuit in a build contest by John G8SEQ



I might even add a small PA to c5W as I note I have some IRF630 salvaged from that same APCUPS mentioned above. For a 137kHz antenna a fishing pole supported wire and base load will be employed. or I might try Finbar GI4DPE (another x band qso) design for a spiral (1/4 wave?) at 8m AGL.

Just today I noted that this was a suggested possible tuner on the LF group lists:



And as I have an almost identical setup I used for a tuner initially I will be using this for my 160m 1/4 wave antenna. The coil on mine is wound over a paxolin(?) former with added tap points, the capacitor on mine is almost identical with 4 x 250pF sections. When in place will add details of my 500kHz station.


Back 22nd January 2008 posted to GQRP:

Re: [GQRP] 500kHz QRP crossband QSOs
Hi Roger (G3XBM),Whilst waiting for my own NoV to arrive I am listening out on 500kHz and like you managing a few x band qso on 80m.Inspired by your comments on GQRP last year and the RSGB conference talks on LF my initial RX were FT897 or FT817 with no modifications. (Advise at the conference was to consider 80m if cross band QSO required).I have an SDR RX on 500kHz based on a softrock I modified with a reused a 4MHzxtal from a PIC project and the divide by 8 option on the board (For those that may ask Tony Parks, KB9YIG will sell a softrock lite V6.2 for just $11 sent to EU and the modifictions can be done for pennies. The 500khz band is just 3khz wide so the whole band activity can be seen on the SDR display, infact I see 480- about 527 kHz! I used axial inductors (a bit fatter than 1/2 W resistors) fora new front input filter. The L are 10uH and 100uH. I used Rocky RX software.If you have a 80m CW setup and can RX on 500kHz as Roger says have a listen in the evenings as some of the operators, there are only about 40 in UK that have an NoV (several are GQRP members) often call for a x band qso on 80m (stating the qsx frequency ) I know many were interested to hear my signal reports as a'new kid on the block' so to speak 500kHz wise.I managed a qso with GI4DPE (Finbar) him on 501.33khz and me on 3533khz. (Finbar has managed a transatlantic qso on 500kHz), amazing when you consider his ERP was 100mW. Similarly with G3ZWH and G3ROO the same night. So far heard/worked themand G3KEV, G3GMH, G3XIZ and GOMRF, cw is the primary mode although hearing some RTTY as well as seeing QRSS in waterfall. I have been surprised at how quiet the band is noise wise compared to 160m or 80m (or it is around me).The signals are easy to copy and maybe just me but the cw is nice and slow.73 Dom M1KTA

New antenna at QTH?

Been agonising over this for ages (2 years+).

Do I need or want a better antenna at the home QTH? Every time seem to operate from home for contest etc it involves putting up a dipole as the vertical (Hustler 6BTV) works FB but just doesn't seem as useful for inter G working on 80m and seems limited to working EU stations only. As soon as a dipole or G5RV goes up the US opens up and there is more DX heard.

The recent windy WX in UK had seen a tree limb came down at the bottom of the garden and it bent literally the vertical over at 60 degrees about 5ft AGL and also took out the dipole support. A new length of Ali tube was obtained and antenna is back up again but thought time to consider the options.

Current thoughts are:

Cobweb
UPDATE HERE:
http://m1kta-qrp.blogspot.com/2008/10/cobweb.html

(http://www.g3tpw.co.uk/ and http://homepage.ntlworld.com/andymuza/G7VOT/Cobweb/Cobweb.html)


Nice small footprint and will fit on gable end of garage or side of house easily!
Downside is long feeder.

Heaxbeam (http://www.leoshoemaker.com/hexbeambyk4kio/general.html)



Gain but bigger footprint. c5m radius
Will fit on side of house but not easily!
Downside is also long feeder.

Simple Dipole for 80m or a fan dipole.



However run into the "wires down the garden XYL and neighbour problems".

Copper Pipe, got some 22mm pipe and 90 degree couplers and end stops or 1/2" heliax (LDF-450) Mag loop.

I have a small vaccum capacitor bought at Friedrichsafen 2007 and a gear box of Mecano Gears and inners from a small hand drill. See this site for one option http://www.qsl.net/hb9mtn/hb9mtn_magnet_80.html

Maybe could build this and put in attic?

Do nothing and stick with vertical and temporary dipoles (maybe end result depending on planning) and add a sloping wire from house to the shack with a tall support at the shack end, would result in about a 50m run which is enough for a 160m 1/4 wave. like this:


The ground system could/would need to be be improved as well so I picked up a few extra ground spikes that were on sale at B&Q.

So bought a couple dozen 5m telescoping fishing poles and will start a 'shoot off' as I will construct the cobweb and hexbeams for all bands 10m through 20m. And a mag loop for 40m and 80m. For 160m I will look at the sloper and any other antenna designs I have seen.

I might end up having to stick with the vertical and a dipole but this might be fun.

As I progress will post the results and which tuners worked best if needed.

My rear garden is larger than most at > 50m long but narrow 15m, It runs N-S with shack at South, house at North. I have 2 large 60ft+ poplar trees next door to the East. No cannot use them I asked but it is tempting to fire a line over them but when windy the tops whip about a lot so any antenna would be shredded or drag the shack with it!
All activity will be QRP only.

NoGaWatt

Every QRP OP needs an accurate qrp meter that will work at 5W and less. Many commercial meters seem to need 5W or more to even move the needle. I had to modify my original meter to be able to show 10W as it was a 100W VSWR....

Back in May 2008 I spent a week with Ken Evans and Ted Bruce (and a few other amateurs) at FDIM/Dayton 2008 and they mentioned the NoGaWatt meter so I thought I'd have to try it.

This is a fine example from N5FC and shows how small and neat these really are:

The project docs are here:


http://www.nogaqrp.org/projects/Nogawatt/nogawattwithnewschematic2.pdf



At the 2007 GQRP rally Henning Mikklesen OZ4XF gave me a pair of dual meters which are high quality dual channel VU meters surplus from some B&O project that never happened. The scale is 250uA FSD and a little more that the NoGaWatt project so I will adjust things a little.

I used a couple of Ge diodes bought from Harrisons (Local repeater group rally at Bottisham, wx was cold and wet that day and did the round trip 20+ miles by bicycle with xyl!) and two 47 ohm (matched from a big batch) 10W resistors that measured 49.2(ish) ohms. I also have a load of 51 ohm resistors and I have another version using a load in series/parallel combinations to obtain 50 ohm. I switched the trim pots for minature rotary pots after proving the construction worked as I wanted to be able to adjust the scales.

In HB style I have used Double sided PCB to fabricate a sloping front box, I was going to try and use the humble backed bean tin (http://www.hanssummers.com/electronics/equipment/bcdfreq/beans.jpg) but didn't have enough as the green bins were just collected and xyl threw out my stash of tins. The meter being almost 4 1/2" across meant this was never going to be an Altoid project.



I initially wound the FT50-43 with 24SWG wire but will replace the single turn with a length of RG174.

I have a load of 50 ohm 100W chip resistors so adding on as a dummy load. Put 4 out just to see if would fit as also available in smaller 10W variety also TO220 so would put them on back with a switch of the VSWR meter and have a dummy load too.

Pics of my construction follow:



I am also playing (right word?) with PIC variations and I have some 2x40 (yes 40) character displays from Diz W8DIZ and I have an initial PIC VSWR working that shows the fwd/rev and VSWR as figures on the left and moving bar graphs. When complete and stable I'll add the details. I am using a 16F874A (same as 16F877A but 1/2 memory).

What to do with some free MAX 74xx chips

PW October 2008 and November 2008 had this article in it for an Active AF filter using the MAX 74xx chips. Now I get free samples of chips from MAX, AD and TI from time to time and I seem to remember having these so did a search and sure enough I do. So another project added to the build list.

2nd option for one of the 1 pole 12 way switches

November 2008 issue of PW dropped on the door mat this morning.

There inside, in addition to the 2nd half of the SMT AF filter (MAX74xx chips but see later posting) P25-29 is an updated (from original design 1987 GW3JGA, JT Lawrence) LCR bridge by G4CFY, Tony Nailer.

1/2 the challange with magazine articles is finding all the components rather than buying the parts I know I have some TL072 (dual op amps) which I will employ rather than TL074 (quad op amp) and pretty sure I have other IC that are suitable to replace the Quadruple exclusive-OR gate (4070) as well as the 10K pot so going to modify the design a little. The chip count will increase but that is not a problem.

The design uses the dimming of two LED to find the NULL point.

I might see if I can improve on that as I have a null point meter, been looking for a use for it as well as a couple of small 1mA panel meters as well as a couple of PIC A/D projects using 2x40 LCD (from W8DIZ) that could be used instead.

You can use bog standard components for the range switch but I also have some multturn pots for 100, 1K, 10K, 100K and 1M so might use those to setup range values. Ditto for the capacitors. Peter at Jobdog sent me some sample SMT L which I am sure might do the job for the L as well.

I will post build pictures as I progress.

Morse keyboard

Probably about as old a PIC project as is possible to find...

Above is the ExpressPCB layout and mask (superimposed).

Bought a PS2 keyboard from Tesco for £4.88 to replace the one on the desk which will now become this. Will use a 5V regulator 78L05 off a 4 x AA battery pack for power connected to the + and - in the above circuit.

No particular reason for building this one just because it can be built.

Now the really cool thing might be to use the other IO lines in the code with the 16F877A to add rig keying and an LCD display? Port C in the code is already included for an LCD.

Will probably use a DIL socket for the PIC or create a PCB mask with the in circuit programming connections included.

The code is from gcbasic examples:
http://gcbasic.sourceforge.net/examples.html

Church Bell Simulator

The first question bound to get asked is what has this got to do with QRP?

Well 2 years ago I used to commute to London on the train and one of the passengers is the manager of a local (to my QTH) church bell ringing group. (Now I am not the least bit religious having been througha Roman Catholic boarding school kind of drums all religion out of you!)

Anyway discussions on the somewhat boring commute every day had to come to his 'hobby' and that was bell rining, not campanology that is hand bells, and the problems he had when newcombers were first starting out. The noise when they get it wrong or when they ding when someone else should have donged or whatever... when practicing they sometimes silence the clapper (think that is what it is called) anyway I am not into the hobby but what interested me was the option to add some electronic sensors to the silenced bells and the signals from these transducers could be fed into a PC/Laptop and interpreted and the PC/laptop could 'play' the bell. So the worst/best group of bell ringers could ding and dong all they wanted without disturbing Mr & Mrs Grumpy Guts who live near the church and started to complaign about the noise of the bell ringing. Far be it fro me to say that moving next to a Church from the 1500's with bells is not going to mean you will hear bells but the parish council stated the bell ringers had to silence operations or only be active at certain times. I think that is the story it was a long time ago....

The idea is not new and you can read about it here http://www.ringing.demon.co.uk/abel/abelface.htm

Anyway enough diversion onto the electronics and radio.

So the sensors on thebelfry are basically IR LED and IR detectors mounted in a little box adjacent to the bells. http://www.abelsim.co.uk/doc/tbellex1.htm On the wheel cage the bells sit inside I will attach two (as the bells ding and dong at 2 places when pulled) pieces of reflective tape. As the bell wheel rotates and passes the tape a signal will be created. I use a 555 timer to widden this signal into a +5V pulse of about 50-100ms and this is then fed into a PIC. There will be 8 of these as this particular bellfry has 8 bells so I will use 8 input lines on the PIC.

The PIC then through the magic of code converts the input signals into a series of ASCII data signals that can be input into a PC/Laptop. I'll cover the why in a minute. Enter the qrp bit. The church being a historic monument and all that means that you cannot then put up wires etc to transfer the signals to the PC/Laptop so I have investigated several different ways of doing it and the easiest was to use (in the UK) licence free 433MHz TX and RX modules so the connection is wireless. This adds a bit of complexity as the serial ASCII signals have to be converted to Manchester code to be transmitted and then decoded before being presented as the ASCII code at the PC/Laptop. As side note is I tried Bluetooth and COM port/Modem signals but it just wouldn't work reliably.

Now why an ASCII data stream... the Bell Ringers use a piece of software called ABEL and this allows the connection to external bell interfaces and the signals to be 'read' so that a simulation of the sound can be created.

All sounds good so far...

Well the sensors are the easy bit.
The PIC code is causing a few headaches but it seems to be working for a single signal and I am about to connect up the 433 MHz TX/RX modules.

The bit in the bellfry will be called Quasimodo and the bit in the bell ringers chamber Esmarelda.

More as project progresses.