Webseite über mein SDR-Projekt

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XQ6FOD
Beiträge: 16
Registriert: 08 Apr 2017, 19:51

Webseite über mein SDR-Projekt

Beitragvon XQ6FOD » 27 Mai 2017, 19:14

Hallo Leute,
gestern habe ich eine neue Webseite veröffentlicht, wo ich beschreibe, was ich mit der RP beabsichtige, was ich bisher getan habe - und auf welche Probleme ich gestoßen bin. Da es immer noch so wenig RP-SDR-Bastler außerhalb von Deutschland zu geben scheint, hoffe ich mit dieser Seite auf Englisch vielleicht ein paar neue Mitspieler zu begeistern. Oder vielleicht schrecke ich sie nur ab mit den da beschriebenen Problemen....!

Außerdem hoffe ich natürlich darauf, daß Leser der Seite gute Ideen haben, wie man die beschriebenen Probleme lösen kann, oder daß vielleicht sogar jemand an dem Projekt mitarbeiten will!

Ihr findet die Seite hier:

http://ludens.cl/Electron/SDR/redpitayasdr.html

73,
Manfred
DJ7PRM
Beiträge: 4
Registriert: 26 Jan 2018, 15:49

Re: Webseite über mein SDR-Projekt

Beitragvon DJ7PRM » 31 Jan 2018, 16:22

Sehr fein!
f6itu
Beiträge: 30
Registriert: 29 Sep 2017, 19:13

Re: Webseite über mein SDR-Projekt

Beitragvon f6itu » 23 Apr 2018, 12:04

Hi Manfred
That's not frightening at all... it is strongly encouraging and tempting

just a stupid question : did you try to change the pair of IRF FET with a couple of FQP13N10 ? these are very cheap switching FET, same category of the IRF series, but have a lower input capacitance

anyhow, this looks really promizing . Thanks for sharing

Marc f6itu
XQ6FOD
Beiträge: 16
Registriert: 08 Apr 2017, 19:51

Re: Webseite über mein SDR-Projekt

Beitragvon XQ6FOD » 23 Apr 2018, 17:24

Hi Marc,

in my test circuit I used those rather antique FETs, simply because I have a bag full of them, which I got for free, several years ago. These are certainly not the ones I will use in the definitive circuit!

There are many FETs with excellent specs, and it's a real problem deciding which one to use, given the many choices. I can't buy any modern parts where I live, so I have to import everything, and it plays an important role what I can get easily, at what price, and at what shipping charge! So a few months ago I made up my mind at ordered a suitable amount of AOT416 FETs, which seem to have good specs and an attractive price. I have used other types of AOT FETs before, in various switching power supplies, with excellent results. I have even tried some in RF power amplifiers, with pretty good results up to about 15MHz! So I'm kind of partial toward AOT.

The AOT416 has a much better ratio of RdsON to gate charge than the FQP13N10, along with high speed, and I bought them for about €1.50 each, including international shipping. They still haven't arrived, though. My country's customs is delaying parcels by four months, slowing down my project. Maybe I get them around June or so...

Manfred
f6itu
Beiträge: 30
Registriert: 29 Sep 2017, 19:13

Re: Webseite über mein SDR-Projekt

Beitragvon f6itu » 23 Apr 2018, 21:06

Hi Manfred
Never heard of "alpha & omega" before. And these FET are definitely better than FQP13xx. Thanks for the tip and the reference.
The 416 is hard to find in Europe, but TME is selling the AOT412 which is very close in term of characteristics
Seems nice for low cost RF amps :-)
Thnks agn.
Marc
XQ6FOD
Beiträge: 16
Registriert: 08 Apr 2017, 19:51

Re: Webseite über mein SDR-Projekt

Beitragvon XQ6FOD » 23 Apr 2018, 22:09

A few years ago I have been playing with the AOT3N50 as an RF amplifier, replacing the often mentioned IRF710 and IRF820. The AOT is cheaper and more powerful. It outperforms the IRF820 in every way, but above 21MHz the IRF710 wins over the AOT3N50. From 1.8 to 15MHz I got a good, stable and clean 70W output from one pair of AOT3N50, with 100V supply voltage.

I also found a FET from Ixys that outperformed the IRF710 in every way, including cost, being usable to 54MHz. Unfortunately it has been discontinued. Most new and better FETs are made available in SMD format only, which makes it harder to dissipate power. Impractical for experimenters.

Manfred

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