Your 2020 builds!

Everything technical about radio can be discussed here, whether it's transmitting or receiving. Guides, charts, diagrams, etc. are all welcome.
Gigahertz
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Your 2020 builds!

Post by Gigahertz » Wed Dec 30, 2020 4:48 pm

Evening Necks!
I was going to revive an old thread but thought it would be different to end this year by sharing your "2020 builds".

So why not post something you've built this year be it: antenna, transmitter, receiver, limiter, RDS or a modifcation to something.

Don't matter if you have posted it before! If you can find the link to the old topic add it to the post if not put the details of the design/circuit diagrams to your post but make it brief. This may give newcomers or older necks who wanted to give it ago the ability to find it quicker.

This will hopefully encourage others who have never posted a build to wave 2020 goodbye!

What do you think?

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Re: Your 2020 builds!

Post by Gigahertz » Wed Dec 30, 2020 4:56 pm

I'll go first!

Corsair SW transmitter design by Dave Martin as found on http://freeradiotx.blogspot.com/2014/04 ... metre.html

I built the Corsette (low power) last year and always said I would be the higher power version so finally got round to building it over the last few days. Produces about 10watts between 6MHz- 7MHz by a crystal which are getting hard to get hold of but they are out there if you look hard enough. The vinyl box was off ebay and makes it look like the old X-band link boxes. Islands on copper board were cut using a drill bit slightly moddifed for the job.

The final is bolted to the enclosure which just about does the job but as it was a experiment to see if works ok, It's not been built for serious use.
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 12:05 am

Excellent work Mr Gigahertz! Neat and tidy! I like it! :)

Despite all the chaos going on around us, I have had quite productive year! Roll out of the Sinus Band 1 TX, Sinus Band 1 RX and the Sinus RDS has been a great success!

I also built a FM Stereo Rig from parts i had lying around which works great! (Experimental purposes only)

I will post some pics!
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 12:10 am

20201224_142804.jpg
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 12:13 am

20201224_142655.jpg
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 12:17 am

20201224_142602.jpg
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Re: Your 2020 builds!

Post by Gigahertz » Thu Dec 31, 2020 1:28 am

Good Job Sinus!

You have been busy :tup

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Re: Your 2020 builds!

Post by nrgkits.nz » Thu Dec 31, 2020 6:11 am

sinus trouble wrote: Thu Dec 31, 2020 12:10 am 20201224_142804.jpg
One of my coder boards complete with my website url on it

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Re: Your 2020 builds!

Post by radium98 » Thu Dec 31, 2020 7:07 am

good work guys :)

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Re: Your 2020 builds!

Post by zulu53 » Thu Dec 31, 2020 11:45 am

Hi Sinus. My congratulations for your
nice and clean work. It looks like a NRGKIT 4W, driving some LDMOS 600W+. I have few questions:

1. Apparently, you are not screening different boards. Don't you have problems with that?
2. It seems you are using an external power supply. Which one?
3. Your fan is being used as an extractor and not a blower. Is this a correct statement?
4. Is there a specific reason to use SO239 jack, instead of N type?
Regards

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Re: Your 2020 builds!

Post by XXL » Thu Dec 31, 2020 4:15 pm

Sinus how comes you leave your designs so spaced out on the pcb ? You could make them so much smaller and neater.

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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 9:56 pm

nrgkits.nz wrote: Thu Dec 31, 2020 6:11 am One of my coder boards complete with my website url on it
Indeed G! :)

Those encoders are excellent quality! Very low noise, great stereo separation and such a clean warm sound!

I have always wanted to get my hands on one since i first saw them on the NRG website.
The PCB itself was given to me but i had to source the parts myself.
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 10:39 pm

zulu53 wrote: Thu Dec 31, 2020 11:45 am Hi Sinus. My congratulations for your
nice and clean work. It looks like a NRGKIT 4W, driving some LDMOS 600W+. I have few questions:

1. Apparently, you are not screening different boards. Don't you have problems with that?
2. It seems you are using an external power supply. Which one?
3. Your fan is being used as an extractor and not a blower. Is this a correct statement?
4. Is there a specific reason to use SO239 jack, instead of N type?
Regards
Thank You Zulu! :)

The Exciter is my version of the Original NRG 5 Watt VFO Running at a reduced output power of around 2.5 Watt.
The PA Is the well known MRF186 mounted on quite a hefty heatsink and set to run at around 80 Watt.

I have not experienced any issues with coupling between stages so far? But yes you are entirely right, Screening is always a good idea to be safe. I will most likely fabricate some aluminium sheet for separation.

The fan as you mentioned is extracting heat from the enclosure. Cool air enters the enclosure through a perforated intake mounted on the lid adjacent to the PA (Hard to see but visible on one of the pics) This allows the flow to be somewhat diverted between both the heatsink veins and the topside of the PA.

The rig will happily run on any voltage in the range of 15V - 24V and is currently fed from my Bench PSU.
I may buy a SMPS (24V 10A) in the future? but not too important.

Again also N-type connectors would be preferable which i may swap out in the future.
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Re: Your 2020 builds!

Post by sinus trouble » Thu Dec 31, 2020 10:52 pm

XXL wrote: Thu Dec 31, 2020 4:15 pm Sinus how comes you leave your designs so spaced out on the pcb ? You could make them so much smaller and neater.
Haha! I see what you mean Mr XXL. :)

The exciter especially is rather large! I guess its old and was etched/built manually from scratch with little resources available.

Now with PCB production widely available, I may re-design it one day?
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Re: Your 2021 builds!

Post by reverend » Wed Jan 06, 2021 3:27 pm

Been working on a new 1W driver board. This is the prototype (which is why there are a few components still on the bottom of the board and the coils are standing proud) and other than needing one extra resistor that isn't on the PCB it works like a dream. It's a half frequency oscillator type. Will also do a good job as a Band-I TX with a few values changed. Waiting for and updated board with the missing resistor present and some minor improvements, and for the prototype Band-I RX boards to be delivered - that's the next project for "Lockdown 3 (the worst sequel ever)"...

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Re: Your 2020 builds!

Post by Albert H » Thu Jan 07, 2021 4:33 am

Looks promising! I think that I recognise that PLL!

Did you have issues with the doubler stage? Did you try to make it no-tune? I've been experimenting with a diode doubler, which requires no tweaking at all. I'm using a Soshin ceramic filter after the doubler stage to give clean drive into the '135 final. I'm getting about 500mW of very clean Band II, with the unwanted products right down in the -88dBc grass!
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Re: Your 2020 builds!

Post by reverend » Thu Jan 07, 2021 9:25 am

The oscillator is based on the old push-pull design (e.g. similar to that in the picture, but obviously with correct biasing and an output for the 2f component) which has the benefit that because the feedback is cross-coupled between the two transistors it kind of 'auto balances'. The use of a toroid as the inductor helps maintain a nice balance too. I haven't had a chance to put the output on the spectrum analyser yet, but at a few tens of metres distant, the only 'f' component I can hear seems to be coming from the oscillator itself. Shielded in a box it's virtually non-existent. 3f/2 seems quite low too - the spectrum analyser will reveal all when I get to it...

It's no-tune other than for needing to set the variable capacitor across the VCO coil. I can make it stretch from 87.5-108 without the variable cap but I prefer to make the VCO less sensitive as it helps keep the PLL reference frequency down below the noise. The 4024/4040/4046/4060 combination works well (as you said it would Albert!) The updated version (boards in the post) uses 3 x 74HC4020 for all the dividers keeping the parts count down (and according to the spec sheets, the 4020 has a marginally higher typical operating frequency too).

Will post a picture of the updated board when I have one working (and the Band-I RX).

Rev
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Re: Your 2020 builds!

Post by Albert H » Thu Jan 07, 2021 12:30 pm

I've used the 4020 too - the 74HC version will usually go to around 75 MHz. Unfortunately, it has fewer division stages, and you'll probably have to cascade them if you want to have a reasonable step size - that's why I picked the '4040. Also, I did a very neat PCB that used three 16 pin ICs (4060, 4046, 4040) and either one (SAB6456) 8-pin prescaler, or two prescalers cascaded (in a 16-way IC hole) for the ~1GHz range - I like my boards to be neat!

The push-pull oscillator with inductive output coupling looks like a neat idea - I might give that a try myself. Did you use a centre-tapped primary? I remember a version of this using a couple of FETs, and it balanced really well with selected capacitors. Agai, this might be something else to try.

I'm all in favour of minimising the number of values of parts in a product - it's one of the elements of cost-effective design. However, you can end up going too far, and start to parallel and series components for values you need.....

What are you using for your varicaps? I'd be inclined to select a pair of 1N4148s for the same forward voltage (which tends to indicate the same reverse capacitance), and use them for the modulation. I notice that there's no bias on the varicaps in your sketch, by the way. I'd also be inclined to try using reverse-biased green LEDs for the tuning diodes - you won't get many MHz of swing, but certainly enough to stay on frequency. Varicap diodes are getting scarce and expensive!
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Re: Your 2020 builds!

Post by Bton-FM » Thu Jan 07, 2021 1:12 pm

Albert H wrote: Thu Jan 07, 2021 12:30 pm I've used the 4020 too - the 74HC version will usually go to around 75 MHz. Unfortunately, it has fewer division stages, and you'll probably have to cascade them if you want to have a reasonable step size - that's why I picked the '4040. Also, I did a very neat PCB that used three 16 pin ICs (4060, 4046, 4040) and either one (SAB6456) 8-pin prescaler, or two prescalers cascaded (in a 16-way IC hole) for the ~1GHz range - I like my boards to be neat!

The push-pull oscillator with inductive output coupling looks like a neat idea - I might give that a try myself. Did you use a centre-tapped primary? I remember a version of this using a couple of FETs, and it balanced really well with selected capacitors. Agai, this might be something else to try.

I'm all in favour of minimising the number of values of parts in a product - it's one of the elements of cost-effective design. However, you can end up going too far, and start to parallel and series components for values you need.....

What are you using for your varicaps? I'd be inclined to select a pair of 1N4148s for the same forward voltage (which tends to indicate the same reverse capacitance), and use them for the modulation. I notice that there's no bias on the varicaps in your sketch, by the way. I'd also be inclined to try using reverse-biased green LEDs for the tuning diodes - you won't get many MHz of swing, but certainly enough to stay on frequency. Varicap diodes are getting scarce and expensive!
The BBY40 can still be had for cheap, that's what I'm using! :tup

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Re: Your 2020 builds!

Post by reverend » Thu Jan 07, 2021 1:20 pm

Hi Albert,

That isn't the circuit I've actually used, just an example (from the interweb) of the push-pull arrangement. I used a centre tapped toroid-wound inductor for the oscillator with a secondary winding to feed the synthesiser. The 2f is taken off from the emitters which are joined together and then go through an inductor to ground. And I use PNP transistors in the oscillator so the coil is at ground rather than at +VCC. 2SA1206 are nice devices for that.

Yes, you have to use 3 x 74HC4020 - one to divide the reference crystal down, one as a 'prescaler' and one as the divide-by-N, the only nice thing is that they're all the same chip, though on my Band-I RX I've managed to get away with just two as the PLL reference frequency doesn't need to be so low. I've got a second synth in development which is on-frequency rather than f/2 using MB501 pre-scalers and the old workhorse MC145151, which together should get to at least 600 MHz. Will be interesting to see how that prototype fairs and how many resistors I've missed off that design... :lol:

I'm using traditional BB809 varicaps for a decent frequency range on the VCO and modulation is applied directly to them.

Rev
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