Ebay DDS VFO Transmitter From Greece

[@digitalbroadcasting4665]

Thank you Steve for this video. In fact there is a 30Mhz LPF onboard. Since this is elliptic lpf harmonics are suppresed even -70db

[@F_Tim1961]

The DDS VFO from Qrp labs is a better deal if you don't want to do modulation and you do want IF offset and the ability to pull RF filter sets in and out (like BPF and LPF). It's preprogrammed and zero SMD soldering is required because the Si 5135 comes on its own board. Downside is it produces a 10 dBm square wave that has to be filtered. The filters cost next to nothing to makeup from kits - about 5 dollars each. Base unit is $32 USD plus postage. It's the best Generic VFO on the market and plenty have been built. Outpot must go through a 100 nF capacitor.. You can't use a mini RF transformer post amp without DC blocking, if you do you will kill the generator kit. Unit comes with an encoder .. No relative of the owner who is BRitish.. A proper 6W Transmitter design can be discovered by looking up the old Retro 40 From SWLabs. No longer made but the schematic is on the web. The only hard to get part is the Modulator transformer. It directly modulates the IRF 530 PA which runs in class C. The retro 40 is a fixed Tx Variable Rx design . NO pcbs available However layout and schematics are all there in the documents. Try the RigPics site for the manual or Google radio manuals with the device name. The micro chip Mosfet driver chip that drives the single mosfet is still available too but is ancient. TEF

[@adriancressy8363]

that modulation capability is not for me. It can cause a lot of noise in your AM transmitter signal. UNLESS you can select CW mode only. I'm fighting with EF Johnson Valiant CRAP VFO's and impossible to get to the circuits in the electron coupled osc.

[@F_Tim1961]

@@adriancressy8363 looked up a EF JOhnson Valiant and they made a 250 W CW and AM Tx many years ago . I believe this is what you are trying to rework. People who have tried to use AD 9850 or 51 based DDS to drive valve RF have found in the past that the output of about 500 mW is insufficient. There is a high gain RF amp sold as a kit for twelve dollars by The Toroid, King (look up exactly that on internet) it uses 12 V supply and could normally be driven by an Ad 9850 based device. Typical power gain is about 100 or 20 dB. Take care you are not connecting the RF into a 300 V Dc circuit.

[@F_Tim1961]

@@adriancressy8363 It's impossible to usefully send a low level AM signal into a class C valve amplifier chain and get any linear signal out. I Believe this is what you have attempted to do with the EF Johnson connection but that's a guess as I don't have the fine details of the connection you made and to what cct. TE Fidler NzL, ZL1MZR

[@WECB640]

Steve, despite the specs stating that harmonics are -70db below carrier, I hope you'll make a video to confirm this. Looks like a nice bit of kit for the experimenter. Thanks for sharing. 73

[@ruhnet]

I was about to comment that $100 seemed a bit expensive, but it does look like they're really done quite a good job with the product. Sounded really good.

[@daviddavidson1372]

He sells an rf amp board also. Am\ssb Sdr 1to 30 mHz 15 watts.. He also sells another DDS board similar to what you have that outputs 20 watts. Best stuff..

[@MikePeace]

Thanks for the evaluation

[@mattmatthes8016]

How about a pair of 6146 for a PA?

[@Radiogenes]

Awesome thank you for sharing😊

[@U812-k7j]

These appear to be not available anymore I wasn't able to find the seller on eBay.

[@F_Tim1961]

ain't that always the Issue with Ebay and similar crappy no bricks and mortar sellers..... Disappear,... reappear under another name . No tech documentation of any sort with the devices sold... Just brillig TE Fidler who has had dealings with the Chinos...

[@F_Tim1961]

There's a guy called Makris , ebay RF seller in Greece Describe it to him.. maybe he can find it for you G Makris I believe . I' m not saying he makes it but the RF community in GR must be fairly small ??