Building a Hendricks 41dB Step RF Attenuator

Two or three years ago I had a browser tab sitting open on the Hendricks 41dB Step RF Attenuator from Pacific Antenna/QRP Kits in California.  For some reason I never ordered one and when I finally remembered that I was going to get one, they were out of stock.

I dropped them an email back in March this year and James told me that they were hoping to either redesign or restock and then in September he emailed me to tell me that they were restocking.  As soon as the kit appeared back in the shop, I ordered one straight away and it arrived just a few days later.

There’s not really much in the attenuator but here’s everything that came in the kit followed by a picture of the circuit board and all the components ready to go.

Hendricks 41dB Step RF Attenuator kit

Hendricks 41dB Step RF Attenuator kit

Hendricks 41dB Step RF Attenuator kit - All the components

Hendricks 41dB Step RF Attenuator kit – All the components

I was struck by the quality of the circuit board.  Very solid, good through hole plating and very decent sized pads on each side.

It didn’t take me long to fire up the soldering iron and get to work.

The first two resistors soldered into the Pacific Antennas QRP Kits attenuator

The first two resistors soldered into the Pacific Antennas QRP Kits attenuator

Back of the first two resistors fitted to the attenuator

Back of the first two resistors fitted to the attenuator

Because the solder pads are so large on each side, rather than rely on solder to flow from one side to the other, I made a point of soldering on both sides.

All the 'vertical' resistors in position

All the ‘vertical’ resistors in position

I fitted all these resistors and then moved on to the ones below the switches.  I worked from left to right and when I’d fitted R3, I realised that I had no more left.  There was no R16 in my pile of components.


I looked around, I checked the bench, I checked the packaging, I checked the floor but there was no sign of the missing resistor.  I checked my component rack but I didn’t have any 270R 2W 5% resistors in there.

I quickly realised I was going to have to find a spare resistor from somewhere.  I can’t remember exactly how it happened but I got into a conversation on a local repeater where I happened to mention that I was a resistor short and a good friend popped up a few minutes later to tell me that they would drop one over to me later that afternoon.  I asked where they’d got it from and they told me it was a local shop.  I was planning to head over to town later anyway so I said “thank you very much, I’ll pick it up myself”.

When I collected the resistor, I looked at it with disappointment.  It was the correct size and value but the style was very different to the resistors already on the board.  Even though the board was going to be mounted in a box, I wasn’t happy with how it was going to look.

The non standard 270R resistor in the attenuator

The non standard 270R resistor in the attenuator

You can see that it’s totally and utterly different.  You can also see that it’s not soldered in, I just couldn’t bring myself to solder it.

eBay called and I found these.

They looked perfect, correct value, correct power rating and correct tolerance.  They came as a pack of five and I ordered them, paying the extra 20p for next day delivery.

About an hour after ordering these, I rolled my chair back and it stalled on something.  I looked on the floor and there was the missing resistor.  If resistors could smile, I’d swear it was smirking at me.

Within thirty seconds it was soldered in place.

All the resistors fitted to the 41dB step RF attenuator

All the resistors fitted to the 41dB step RF attenuator

The next thing to fit was the large slide switches.  These are big and chunky and feel very positive when chunked backwards and forwards.  I fitted them all with no problems at all except somehow (and I genuinely have no idea how) this happened.

The broken switch

The broken switch

I tried to find a replacement switch locally of the same style with no joy so I emailed James to ask about getting a spare.  James was very helpful and just a few days later a care pack arrived from California.

Two spare switches

Two spare switches

Because I’d done such a good job of soldering everything in, getting the broken switch out was a nightmare.  It took me a good half an hour of working with both a solder sucker and some desolder braid.  It goes to show the quality of the board that I was able to spend so much time on it with a hot soldering iron and not damage it at all.  I’ve never used desolder braid before but that and the solder sucker eventually did the job.

The circuit board showing where the switch was removed (click for a full size version)

The circuit board showing where the switch was removed (click for a full size version)

With the broken switch removed, I fitted one of the replacements which left me all ready for the next stage.

Hendricks 41dB Step RF Attenuator PCB all built and ready to go

Hendricks 41dB Step RF Attenuator PCB all built and ready to go

The next stage was testing so I hooked up my DVM and checked the resistances were all correct with the associated switches.  All looked good.

After this, it was time to prepare the box.  The supplied box has a nice brushed finish and  decided I was happy to leave it like that rather than paint it.  There are some nice decals provided for labelling and the instructions recommend spraying the box with “Krylon clear” first.  This is a USA brand of lacquer spray and not available in the UK so I sourced this alternative from Wilko.

Wilko clear lacquer spray

Wilko clear lacquer spray

After a couple of minutes shaking and spraying, the box was left to dry for 24 hours.

The box, freshly sprayed and drying before applying the decals

The box, freshly sprayed and drying before applying the decals

This looks fine but once the lacquer dried, it didn’t really look very attractive.  I mentioned this to a friend who very kindly offered to hydro dip the box and lacquer it for me.

Once it was all done, I assembled everything into the box for testing.

The finished attenuator

The finished attenuator

It’s quite a dark finish but I think it looks good.  I used my analyser to test the actual attenuation and on 40m, it’s within half a dB or so of specifications and so this will be a useful addition to the shack as it’ll allow me to match the output of my two WSPR transmitters for proper aerial comparisons.

Considering the complexity of some things I’ve built over the years, this should have been a simple build.  It just goes to show that the gremlins can creep into anything and everything seemed to go wrong with this one. I’m just glad it’s finally completed and working as intended.

Posted in Amateur radio, Construction | Leave a comment

Shack wallpaper

Back in 2011 while I was working my QSO365 project (the reason why this blog started), I reached 100 DXCC entities worked and although I applied for the award, I don’t think I ever actually posted the certificate on here.

The general DXCC award is for the “mixed” category which means that you’ve worked and confirmed contact with one hundred different DXCC countries (known as entities) using any mode or band.  There are also certificates available for individual modes (phone, cw, digital) and bands.

Naturally, the first award I applied for was mixed and since then, I’ve added some extra certificates to my collection.  Stickers (or endorsements) are also available for additional entities worked and confirmed.

When I got my first certificates, I put two of them in frames but the frames really weren’t very pretty and I didn’t bother hanging them on the shack wall.

Earlier this year I decided I really ought to update my award account on Logbook of The World and applied for some additional certificates and endorsements.  I also found some much nicer frames and ordered those as well.

So here are three of my DXCC certificates in the new frames.

G6NHU DXCC certificate - Mixed

G6NHU DXCC certificate – Mixed

G6NHU DXCC certificate - Phone

G6NHU DXCC certificate – Phone

G6NHU DXCC certificate - CW

G6NHU DXCC certificate – CW

I’ve actually got eight certificates for different combinations  but I’m not going to frame all of them as I simply don’t have enough space to hang them all.

At time of writing, I’ve got the following number of entities confirmed:

Posted in Amateur radio | Tagged | Leave a comment

Working duplicates in a contest

When I work a contest, most of the time I’m calling CQ and I always work duplicates.  If someone calls me and my log flags that they’re a duplicate, it doesn’t bother me in the slightest, I work them again.

Some operators flatly refuse to work duplicates but I think that’s a mistake and I’d like to explain why, from both the running (CQ) side and when operating S&P.

In a contest earlier this year, one station called me four times.  Each time I worked him.

When the scores were published, the contest also published the UBN log checking report (UBN stands for Unique, Busted, Not in log).

I decided to download the UBN for this particular station and see why he worked me four times.

Here are the four logged QSOs.

0014 21000 G6NHVP G – 0 Busted call, should be G6NHU
0018 21080 G6NHU G + 2 *
0128 21080 G6NHV G – 0 Busted call, should be G6NHU
0197 21080 G6NVT G – 0 Busted call, should be G6NHU

He logged my callsign incorrectly three times (in fact his log was absolutely full of errors) but if I’d refused to work him after our first contact, I wouldn’t have got the points for the QSO.  It’s generally quicker and easier to work someone again than it does to reject them as a duplicate.  The contest adjudication software will pick up on any duplicates and I don’t know any contest where dupes are penalised in any other way than not counting for points.

It works the other way round as well – When operating S&P, I try not to call people twice but occasionally it might happen if I misread their callsign or make a mistake logging it.

In the CQ WW SSB contest a couple of weekends ago, I tried breaking a pileup to work one of the rarer stations and as far as I was aware, I didn’t manage to beat the pileup and I gave up.  A few hours later, I tried again and this time got through only to be told “we’ve worked before”.  I can only imagine that he picked my callsign out but due to QRM, I didn’t hear him reply.  Of course, I didn’t give the exchange so it must have been automatically filled in by their database (it’s fairly obvious that a G station is in zone 14).  In this case, I was lucky enough to be able to get back and say “you’re not in my log, can we work again please” and we did complete the QSO.  It would have been quicker for him in the first place to simply work me again and not try and bounce me as a duplicate.

It’s quicker to work a dupe than to faff about rejecting it and by not working a dupe, you could be doing yourself out of the points for that QSO.

Please work duplicates.  They might be in your log but there’s a good chance you might not be in theirs.

Posted in Amateur radio, Contesting, Operating tips | Tagged | Leave a comment

DMR – My thoughts about Digital Mobile Radio

I’ve written a couple of times in the past about various digital voice modes and if I’m honest, I’ve been quite scathing of them.  I make no secret of the fact that I’m very happy to use repeaters for local natter but don’t like the idea of linking remote repeaters together via the internet to work “DX”.

When I use D-STAR, I tend to unlink the local repeater from the reflector and call through it to see if any locals are listening.

I’m a founder member of the Martello Tower Group and we run a number of analogue and digital repeaters.  We recently moved GB7CL, our DMR repeater to a site just a couple of miles away from where I live and I’d openly said that once that happened, I’d get myself a DMR wireless.

I’ve now had a DMR radio for about a month and have spent a lot of time sorting out the configuration and learning how to use it – It’s quite a steep learning curve but I found a base “code plug” and tweaked it slightly to suit my requirements.

The obvious comparison is with D-STAR.  The first thing to notice about DMR is that the audio is significantly better than D-STAR which is down to higher bandwidth and a better audio CODEC.  It’s not uncommon for me to hear someone I know working D-STAR and barely be able to recognise their voice.  That’s not the situation with DMR, everyone sounds as I’d expect them to do.

What I like very much about DMR is how the Regional “Talk Groups” work.  DMR repeaters are centrally controlled and certain talk groups are linked together by region.  For example, Talk Group 840 links together repeaters in Ipswich (GB7AL and GB7MK), Clacton-on-Sea (GB7CL), Tring (GB7CT), Norwich (GB7DS), Pointon (GB7FU), Halstead GB7HA), Attleborough (GB7ND), Peterborough (GB7PE), Cambridge (GB7PY), Leicester (GB7SK) and Bury St. Edmunds (GB7WS).

In practise, if you transmit on the East England Talk Group 840, you’ll be relayed through all the above repeaters simultaneously.  This is very much how we used to have the analogue repeaters GB3CE and GB3CL in Clacton-on-Sea and Colchester configured except we were linking via RF and not an internet backbone.

I have no problems with this form of linking, in fact I think it’s fantastic to have multiple local/regional repeaters joined together like this.

In addition to this, there’s a larger Talk Group (801) covering the whole of the South East which consists of twenty repeaters all linked in the same way.

There are other regional Talk Groups configured and the best way to demonstrate this is to have a look at the link on the DMR-UK web site here where you can sort the list by regional talk group to see exactly what’s in each one.

In addition there are other talk groups designated as World Wide, UK Wide and Europe where. as the name suggests, anyone calling through them will be relayed through every repeater in the group.

However you don’t have to access multiple repeaters at the same time.  Each repeater has two local talk groups which are entirely self contained so they can be used in exactly the same way as a traditional stand-alone repeater.

This page gives a list of all the talk groups which are available on each repeater.

Another nice feature of DMR is the ability to automatically ‘roam’ across the network so if one goes out of range of one repeater, the radio will automatically switch to another one.  As I don’t have a DMR wireless in my car, I’ve had no experience of this but I have listened to stations driving around who have commented that they’ve just roamed to another repeater.

Each repeater has two “Time Slots” (TS).  Effectively this means that two QSOs can happen at the same time, doubling the capacity of the repeater.  TS1 is used for national and international talk groups and TS2 is used for local and regional talk groups.

The above probably sounds incredibly complicated and when I first switched on my DMR radio, I was totally overwhelmed.  I spent a lot of time reading the DMR-UK site and along with listening around the network, I’ve quickly picked it all up and I’ve got my head around most of it.

Whereas D-STAR radios are almost exclusively manufactured by Icom (except the recent Kenwood TH-D74E), there are a few different DMR manufacturers.  In the UK the most common seems to be the Tytera (TYT) UHF MD-380, available from China for as little as £70 via eBay or a little more if you buy from a supplier based in the UK.  There is also a recent mobile dual band radio, the TYT-9600 although I understand that’s going through some teething problems because it’s so new.  At time of writing this is only available from one UK supplier.

I’ve often heard DMR described as “The poor man’s D-STAR”.  Although it’s significantly cheaper to buy a DMR wireless than a D-STAR one, I don’t think that’s a good comparison.  Compared to D-STAR with the random linking of reflectors and the relatively poor audio quality, I think I prefer DMR.

I like the way the network is configured centrally into regional talk groups, I like the roaming feature, I really like that by selecting the local channels, it can just be used as an unconnected repeater.

With all these positives, is there anything I don’t like about DMR?  I’m not a great fan of the huge learning curve.  I can see that it can be quite complicated and can understand why some people aren’t able to get their head around it.  I think that by forcing myself to be a DMR SWL for a good few weeks, I’ve been able to get a decent grounding in how it works and how to operate it.  I don’t like using things I don’t understand.

A few days ago, I visited an area which I don’t have programmed into my DMR radio.  Because of the complexities of setting these things up, I couldn’t use it.  Unlike an analogue radio, I couldn’t simply tune my wireless to the local repeater, set up the CTCSS tone (or whistle at 1,750Hz) and speak through it.  It was effectively useless.  This is the same for D-STAR as well though, it’s not just a limitation of DMR.  At least with D-STAR I have the entire UK repeater network configured and using the built in GPS, it can always find the closest repeater to me.  I don’t think this feature is available on any DMR wirelesses yet.

I’m also quite frustrated by the terminology that seems to be coming into amateur radio from the commercial side.  Everyone talks about a “code plug” which is really just a list of frequencies, offsets and memories and links them together.  We’ve been doing this for years, programming memories and setting up radios but for some reason we’ve now adopted a commercial term.   Also, there’s a “colour” linked to each channel which is the CTCSS tone.  Why not just say that you’re programming the radio and using (103.5 or whatever) CTCSS?

The World Wide and Europe Wide talk groups don’t interest me in the slightest.

What radio did I buy?

Despite saying that I don’t like handhelds, I bought one.  I didn’t go with a very cheap Chinese import because I’ve heard too many horror stories about them arriving broken or failing after just a few weeks and being impossible (or prohibitively expensive) to return them.  I bought mine from a UK supplier via Amazon because I figured that I’d have a better chance of any returns if it arrived faulty or stopped working within the warranty period.  I also had some credit on Amazon so the actual cash I had to spend made it a very reasonable price.
I wasn’t prepared to pay £280 for a dual band mobile radio for a mode I may have hated and I’d also read too many bad things about the MD-9600 and the poor firmware to consider one just yet.

This is what I bought.

TYT MD-380 DMR UHF handheld

TYT MD-380 DMR UHF handheld

Posted in Amateur radio, D-STAR, DMR, FM, UHF | Tagged , | Leave a comment

Building a JYE Tech Cap Meter 060 Kit

One of the new local Foundation licence holders recently did the Intermediate course and exam and as part of her practical assessment, she built a capacitance meter which I’m sure helped her pass the course.  Well done, Caroline!

I fancied doing the same as it’s a handy piece of test gear that I’ve never owned.

The meter in question is from JYE Tech although I bought it from Hobbytronics in the UK for just over £14 delivered which I thought was an absolute bargain.  It arrived the day after I ordered it which is really good service.

There’s not much to say about the actual construction.  At 18:00 yesterday it was a bag of parts like this:

JYE Tech Capacitance Meter DIY Kit

JYE Tech Capacitance Meter DIY Kit

The circuit board is clearly labelled and easy to work on.

Circuit board for the JYE Tech capacitance meter kit

Circuit board for the JYE Tech capacitance meter kit

The kit was very straightforward to build, although there was a lack of detailed instructions.  They simply say “fit all the components on the board, making sure to get the two electrolytic capacitors in the correct way”. The resistors are tiny and I struggled to see the markings on them which I suppose is one of the downsides of getting older.  I ended up using my DVM to double check the values.

Despite that, it was a simple and straightforward build and less than an hour and twenty minutes after starting, I had a fully working capacitance meter sitting on the bench and measuring a 330uF electrolytic.

My new capacitanceometer

My new capacitanceometer

It’ll probably get boxed at some point and I’m quite sure that it’ll be a useful piece of test equipment to have on the bench.

Posted in Construction | Leave a comment

My first new DXCC entity for over eighteen months

I’ve not been specifically chasing new DXCC entities for a while and because of this, I’ve only picked up four since 2015.

I know there’s been some interest surrounding the 3C0L and 3C1L DXpedition to Annobon and Equatorial Guinea respectively over the last few weeks and although I missed out on working 3C0L, I was keen to work 3C1L.  I’ve heard them a couple of times over the last two or three days but not been able to work them.

I’d left a browser window open on DXWatch set to 3C1L and as I took my morning break, I saw that they’d been spotted on 17m.  It only took a few minutes of calling before I heard my callsign coming back.  The last letter was blatted by noise a little so to ensure that they’d received me correctly, I called again and received the acknowledgement back.  You can hear a recording of this QSO on my Audio Snippets page.

Only an hour or so later, I was passing the shack again and glanced at the screen to see a single spot had just been reported on 12m.  I thought this was worth a try so tuned to their frequency to hear a weak signal.  I set my split to just over 1kHz and called them.  To my astonishment, I worked them on my first call.

A similar thing happened this afternoon.  I saw they’d been spotted on my favourite band, 15m so I found them and started calling.  They weren’t very strong and there was a lot of QRM but I’m pretty sure that within a couple of minutes, I’d worked them for a third band slot.  Out of the three, this is the one I’m most happy with (assuming it was a good QSO).

This is my first new DXCC in the log since April 2016 and takes me to a total of 272 separate DXCC entities worked.

Posted in Amateur radio, DXpedition, HF, New DXCC | Tagged | Leave a comment

CQ World Wide DX SSB Contest 2017

Strange as it might seem, I’ve never put in a good solid single band entry into the CQ WW SSB contest.  If you look at the recent addition to this site, my contest results page then you can see that I came third (out of three) in 2013 for my 15m entry, first (out of one) in 2012 for my 40m entry and second (out of three) for an all bands entry in 2011.

With conditions the way they are at this point in the solar cycle, I went into the contest this weekend with an open mind.  I wasn’t sure what I was going to do, whether to concentrate on a single band or go for an all band entry.

I started off on Saturday morning having a quick tune around 40m and working one or two stations before switching to 15m for half an hour or so.  My tactic all weekend has been simple, tune the band from one end to the other and work everything I can manage.  15m started off quietly so I switched over to 20m and did the same thing.  When I’d done on 20m, I moved back to 15m and really, didn’t move very much from there until the end of the contest apart from half an hour on 10m and a handful more QSOs on 40m.

Normally in contests, I’ll find a frequency and call CQ but I had already decided that I was going to operate entirely by search and pounce this year.  I’d spent some time ahead of the contest sorting out my logging and had got SkookumLogger set up exactly as I wanted.  Once it’s set up and working, it’s really good and although it looks complicated with all the windows on screen, it’s actually very straightforward to use.  Here’s a screenshot of it taken shortly after I finished operating.

SkookumLogger at the end of the CQ WW SSB DX Contest 2017

SkookumLogger at the end of the CQ WW SSB DX Contest 2017

This small image really doesn’t do it justice – Click it for a full size version.  You can see I have all the important info, a map (showing my current beam heading), live scores, live rate tracking, a checklist of zones and countries and everything that you’d need to know while working a contest.  Although I was connected to the DXCluster, I really used the cluster windows as an indication of what I’d already worked.  As I tuned through the band, if I came across someone who was highlighted in red, it meant I’d worked them before and didn’t need to type their callsign in to check.

Individual band statistics

Individual band statistics

This window shows the breakdown of each bands – The band I was most interested in was 15m where I made 264 QSOs, worked 65 DXCC entities and 19 CQ zones with one duplicate.

One of the great things about SkookumLogger is the ability to automatically control a rotator.  A week ago I bought a rotator interface to use with my Yaesu G-1000DXC and I was amazed at how useful it was and how well it worked.  I do appreciate that HF beams generally have a wide beamwidth but it made a real difference to always have the aerial pointing in the right direction.  As I entered callsigns into the log, the aerial would turn automatically.  If I wanted to stop it spinning, there’s a simple keystroke that aborts the movement.

Easy Rotor Control ERC-Mini

Easy Rotor Control ERC-Mini

Although I like working the big contests, I do find it frustrating that many of the big stations can clearly transmit a lot further than they can receive.  I missed quite a lot of multipliers due to them simply not hearing me.  I found myself replying to continual CQ calls a few times and just not being heard.  I could understand not being able to break pileups (and that happened a lot) but not being heard by someone who is showing 40dB over S9 and has no other callers is really frustrating.

15m did open nicely to the USA and South America in the afternoon but only for a few hours, closing pretty much as the sun vanished.  Compare this to what I’ve done in previous contests and there are many distant countries missing – Japan, China and Australia, to name just three.  Also noticeable by their absence from my log are quite a few European countries that I’d expect to work.

Finally, here’s a map of stations worked on 15m during the contest.

Map of stations worked by G6NHU on 15m during the CQ WW SSB contest in 2017

Map of stations worked by G6NHU on 15m during the CQ WW SSB contest in 2017


Posted in Amateur radio, Contesting, HF | Tagged | Leave a comment