NM5DV Softrock SDR Blog

I have added the attenuation circuit to the ouput stage of my softrock, just before the antenna connector.

It provides -3db of attenuation, basically cutting the power in half.

So if the softrock is putting out 1 watt (more on this later) then I should be pushing a whopping 1/2 watt or 500 mw.

I am very pleased with k6hx’s grabber I can really use it for testing because my signal is usually decently nice on it. So last night I had a bit of spare time and I took a look (thank you daylight savings time) at his grabber,

after I saw my signal was looking good I switched on the attenuator.

Here Is where I turned the attenutor off.

I think my experiment might have been slightly flawed in that the propagation was a bit different when I turned the attenuator off.

I will rerun using less attenuated time and bit earlier in the evening (i got busy with the kids)

7 ’s de nm5dv (vincente spilled bubles on the three)

Addendum:

After consulting both k6hx and kc8bll on erp of the system we determined that the total erp of the softrock with the Barker and Williamson ac130 and feed line losses is roughly 600 mw on 30meters.

So after the -3db attenuation I’m looking at a whopping 300mw of erp.

QRZ.com show the distance beetween me and k6hx at 913miles. Not too bad.

Here is the attenuator circuit. I borrowed this from a Doug DeMaws circuit. This is better than the pi circuit approach because it uses standard resistor values. It is a T network attenuator

73s de nm5dv k.

Well I got my replacement parts for the softrock, Tony kb9yig is always good about gettimg me odds and ends that I have fried.

I order 2 fst3253

2 lt6231

2 7fac74

This is jsut some op amps a mixer and divider chip that i thin was messed up.One nice thing about smt stuff is that its pretty easy to desolder. If you had a 16 pin thru hole ic it would be a realy tough cookie to get off the board in one piece.

heres how I desolder a chip:

Hit it with some braid or the sucker now and it will be good as gold. The chip is also still usable As I discovered that the same problem was there after I put the new chip on.

Basically the diver is not showing the poer output voltages… To be continued.

73’s de nm5dv.

There’s a new sheriff in town and his name is kk7cc. He is running a grabber out of Las Vegas Nevada.  I’m excited because this about one perfect skip for me so I should be able to use it for testing out my stuff. Sometimes when the propagation is bad I cant see myself on any of the grabbers and I often wonder if I ’m getting out there.

Heres a screenshot from this morning :

Hes running an old k2 but he says its drifting around a little and hes working on stabilizing it. Good luck and thanks for the grabber.

Addendum:

Heres the link http://www.qsl.net/kk7cc/kk7ccgrabber.html

I have been wanting to write this post for a while, I feel that by building the softrock rx/tx v6.3 from a kit that I don’t really classify as a homebrewer.

In my mind a true home brewer is somone that takes a thought and puts it on paper, molds it then builds it and puts it on the air. I did not do this.

Where do we draw the line ? This is a personal choice that we must each decide.  One person might believe he is a home brewer if he builds a cw rigfrom a kit. Another person might draw the line at getting ahold of a schematic and building it. A third person will only be happy if he builds froma a schematic but makes changes that will make the device his own.

Not me, I have never called myself a homebrewer, I will do that when I build a transciever entirely from scratch.

Perhaps I am hard on myself, if I am not who else will be. I do not know where these feelings come from, I remeber studying for my technician test and hearing about homebrewers and thinking that it was not for me. I have built kits and for the majority of people this is quite a challenge. I have freebuilt and modified my softrock and still I am not content with my accomplishments.

As I write this JFK’s speech comes to mind :

 ”We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too. “.

How true decades later and so much less important, I choose to do this not because it is easy but because it may very well be the most difficult thing my mind has set out to do.

I love my softrock. I have built it and fried it and rebuilt it ( I should give it a name). But I will not be happy until I have a true home brew qrp rig on the air.

Do not let my goals affect you, If you are content building kits, downloading and building schematics then by all means do it. If nothing else you will gain your own self respect and learn a little. I will not belittle this act it is not easy and you will have raised yourself above the majority of hams who are appliance operators. Purchasing and operating cookie cutter stations. If you are here, then you are obviously different, go and listen to JFK’s entire speech and relive a time when discovery was a goal and exciting.  Then perhaps this blog post will creep back into your mind and you will decide to raise your own personal bar.

In addition kits are an excellent way for new builders to get acclimated to some of the more advanced soldering and toroid winding skills as well as understanding the stages of recieve and transmit. I personally recomend the small wonders lab kits. They are basic and the details make you do a bit of your own research to try and understand what the rig is doing.

In the end its all about fun, enjoy the hobby and exercise your melon.

73’s de nm5dv k.

1 watt was just doing too good, after receiving yesterdays signal reports, and getting a few minutes to install my attenuator lat night I did some tests this morning.

I put the attenuator after the lpfs and jumpered it so that I can turn it off and on when I want. I stole the design from the amp I’m building.

It is a -3 db attenuator which should take out about half of the output power. This should put me right at about 400 mw when you include the tuner and antenna loss.

I took a few before shots on the grabbers but I was interrupted, I’ll try and post a few of these soon.

Well I’d like to thank Ted aa5ck for sending in a signal report this afternoon, it’s always nice to know your getting out there.

He attached this picture:

me and wa5djj talking to the neighbors.

Thanks Ted, glad to see some qrss listening stations out there..

Oh, on that note :

I installed the divider chip backwards in the softrock lite II and it fried it so it might be a few weeks before the grabber is up on the air.

73’s de nm5dv k.

Addendum:

Just thought it might be neat to give a snapshot in time type thing:

here is k6hx in El Sobrante California (San Fransisco)

Here is w1bw up in Concord Ma.

k

After a nice day of operation on 30m I decided that the rig was working well enough to attempt to destroy it again.

I removed the zip wire that was connecting the output board to the antenna connector and replaced it with some nice rg-174.

pre new cable.

I opened up power sdr for the first time in a long time. I messed with it an confirmed that it was able to key up via vox and that I was on the right frequency. I had intended to run it all day today but it started acting weird and I didn’t feel confident in its ability to run without me babysitting it (while I’m at work). One of the nice things about power sdr is the ability to play wav files out. I am hoping to be able to play the wav file that k6hx made for me of my cwfsk call sign. I would also like to print a zia in there somwhere just to get fancy with it.

I also hooked the rig up to my z100 autotuner as the finals were slightly hotter than I liked. I’m sure this will burn off a bit of rf and attenuate the signal unfortunately there’s no way to calculate the loss. After I hooked it up the finals were definitely cooler.

I began to build the -3db attenuator onto the output board and it was about 12:30 that my son decided I needed to come to bed so the resistors are awaiting their new life and the rig is still at 1 watt. Hope to get it on there tonight.

I woke up this morning and cleaned the shack and fired up powersdr to see if it would play the wav file but it claimed that it had an improper sample rate. So I made a recording and sent it over to myself to analyze what it would want and if I can figure it out I’ll convert k6hx’s file and try and play it for a bit today.

that’s it … beacon is on the air and all sealed up in its little box running nice and cool..

73s de nm5dv

The first project that I built was a Small Wonders Lab sw+ for 20meters. Its an awesome little cw rig that comes as a kit.

I built it in my normal flair, meaning that gettign the kit and building it was not an option. I made it my own. I built it into a custom enclosure, I added the k1el keyer and built it into the enclosure, I added a tayloe swr indicator as well.

It is a bit more complicated than your usual cw qrp rig.

I have been using the k1el part of the rig to key the softrock. The other night as I was checking the ouput of the softrock  I wanted to see what sort of s levels I would get from the sw+. I plugged it in an keyed up and immediately noticed that something was wrong. I checked the final and It was smoking hot. Smoked again!!….

such is the life of a homebrewer (even if I consider myself a home kitter now, its a start).

So I’ll have to add this to the list of things to be fixed. I have set a goal of having the rig running by field day.

73s de nm5dv

Well it took two weeks to figure out what I had broken. Even now im not sure. But after plugging in the 30 m paf improperly and smoking the trace on it, I soldered a piece of magnet wire in place of it. After that I noticed that the Icom 718 was rxing at 20 over (whatever that means).

Sure enough once I asked k6hx to see if he could see me, he saw me. He told me where I was at and I was able to get myself back into the right place.

So last night I decided that I would follow best practice and put in the 30 meter lpf. It actually worked, and I even gained an slevel or two.

(note extra space for the attenuator)

So here is the revised project list :

1. Fix the 40 meter paf (I think it has a fried transformer)
2. Attenuator for the output filter board.
3. Troubleshoot the softrock lite II
4. Amp for the softrock (pcb design)
5. Computer and antenna for the softrock.
6. Work on the sw+ 20m (personal goal to have it functional for field day)

I’ll Post some pics in a few.

So as I was happy to just be getting back on k6hx’s grabber, as I was checking in on irc last night Mark told me that they had spotted me over in Belgium right above wa5djj.

So Thats a pretty good feeling except for the fact that as far as qrss goes I am running twice the legal limit.

I am going to work on the output board a bit and get my level down to an acceptable 1/2 watt.

I also feel pretty guilty about running a kit, my true home brew oscillator is always floating around in the back of my mind.  I will have to start working more seriously on it.

Update as I was writing this this morning I was waiting for k6hx’s grabber to start picking me up. wa5djj showed up nicely and I didn’t see myself. When I came into work I took a quick peek and here is what I saw.

Theres me and wa5djj pushing  the 30m grayline nicely.

I also wanted to add that I stuck a headphone jack that I had purchased for the softrock lite II inside the keyer on the front of the rig And for the  first time in a very long time it is running with the lid on and all sealed up (sort of a personal triumph)

73s de nm5dv.