What's the fastest you've got an nrg type vfo to run

[jvok]

Curious to hear from anyone who's messed about with the nrg vfo circuit on higher frequencies above the fm band. Whats the fastest you've got it to run?

Thinking about ideas for band iv links

[teckniqs]

The VFO version should power up pretty much straight away, going from memory.
.....Are you worried about a five minute delay of white-noise, or something?

[jvok]

By fastest I mean highest frequency

[sinus trouble]

I have never tried it? But i do know that Stephen (NRG) used to sell Band III VFOs!

So i would guess they would comfortably run at 200Mhz or more if designed correctly?

[Albert H]

I've done a version of that oscillator that ran at over 500 MHz, which used Lecher Lines for the coils, but I didn't have it "free-running" - it was stabilised by a PLL, using a TSA5511. The amplifier stages had to be re-designed, and I ended up using grounded-base 2N3866s for two stages, feeding a PT8811 for about 4 Watts out.

[jvok]

What transistors did you use at 500mhz albert? Did it still work with bf199s and bf245s?

[Albert H]

I used a pair of BFR91 for the oscillator, and the frequency sample was taken from the stage after the oscillator, and fed straight to the PLL IC RF input. The tuning varicap diode was controlled through a low noise transistor (running from a 30V auxiliary supply).

[Persona Non Grata]

I have never tried it? But i do know that Stephen (NRG) used to sell Band III VFOs!

Shame nobody seems to now ?

Ive always thought Band 3 made more sense for linking than Band 1

[Albert H]

The problem with Band III these days is that it is filled with DAB and PMR.

We used to use frequencies around 200 - 210 MHz (a favourite was to use a 48MHz crystal multiplied by 4 for the receiver injection oscillator, for 202.7MHz). The link transmitter was (usually) a TTL-based PLL at 22.52222MHz driving two cascaded triplers, then a pair of 3N3866s in parallel for about 2 Watts out on 202.7MHz. I used to match them into 75Ω, so I could make use of the plentiful, disused Band III TV Yagi aerials that were on every building!

When DAB started on frequencies around 200 MHz, we moved our links up into Band IV or even Band V. Again I used 75Ω feeders and TV aerials, and this is still (usually) my favourite kind of point-to-point RF link. These days I use a TSA5511 PLL IC and a PIC in the transmitter, and the receiver makes use a a PLL-tuned TV tunerhead module (usually UV616). Even with very low power, it's possible to get long range links (in stereo if you want) because of the high gain of a 20 - 30 element TV Yagi!