NE602A integrated cct.: experience, anyone?

[Skywave]

I'm in the initial stages of researching options for a small home-brew project which will require a VHF mixer with low-level inputs (millivolts range) in the 100 ~ 150 MHz region, both input ports: the NE602A looks like a suitable device for that duty. But I have no experience of this device: does anyone here have such experience with it and can pass on any useful remarks, hints, etc. that are specific to this device? (I say 'specific' since I am quite well acquainted with general constructional practices at those frequencies).

Thanks,

Al. / Skywave / Sept. 24, 2014 //

[Radio Wrangler]

The NE602 is only available now in derivative variants, but not much has changed.

It's described as for use to 200 MHz or so, but it's really designed and specified for use converting 45MHz IFs downwards in dual conversion radio receivers.

The local oscillator which is buitl in is nothing more than a single transistor.

The circuit isn't capable of handling large signals, so it will likely be the dynamic range bottleneck of your design.

It's easy to slag off the Ne602 but it does seem to work better than you'd expect. There are lots and lots of HF receivers in QRP rigs and magazines based on it. G-QRP 'Sudden' for example. Sudden doesn't mean abruptly, George Dobbs church was in an area of Rochdale called 'Sudden'.

By 150MHz, it's going to be pretty much on its last gasp.

At those frequencies, dual gate mosfets like BF904 will be in their prime, and there are many diode rings to choose form (Minicircuits eg ADE series or the TFM-2)

Analog devices and Linear Technology inc have wider band transistor tree mixers.

Without knowing more of the application, there's only guesswork.

David

[Biggles]

There is a comprehensive application note on this device (I have it somewhere) but my experience of using them is that for VHF work they are a bit limited. Unless you use a xtal controlled VFO, they drift a bit (or at least mine did) and as RW says, they can overload. I had difficulty getting the on board oscillator to run correctly with a crystal and went for a separate oscillator/multiplier strip. They are relatively simple to connect up, although I have always used them in the unbalanced mode. I have various past projects that use the 602 lying around unfinished in the shack, probably because they were difficult to get working properly, but that may just be down to me. Plenty of magazine projects are around which use these chips including a 2M receiver that either Ramsey or Maplin did at one time. I'm not sure if they are still available. I have never seen them used in commercial equipment. I think the NE612 may be a very near equivalent if you can't find a 602. I could find the application note number if you are interested.
Alan.

[Restoration73]

You may wish to investigate the TDA1062 as well.

[turretslug]

The "similar but different" SO42P?

[Skywave]

Just an interim comment to say "Thank you" to all who have responded so far: all remarks noted and inwardly digested. I may return to this thread later, depending on further research and (possible) input from other members.

Al. / Sept. 25, '14 //

[ukcol]

Hi Al,

You have probable seen this document but in case not...

[Skywave]

Thank you, Colin. And no, I haven't seen that before. Up to now, I've only looked at the datasheets on the 'Net. That doc. looks very enlightening: I will study it in detail.
Thanks again.

Al. / Sept. 26, '14 //

[Al (astral highway)]

Hey Al, does this (see attachment) device, LT5512, look promising? It's shown used as a downmixer, but doesn't have to be... However, no experience of it, just something I bumped into.

It's good to see that your project-ing again! Let us know how you get on, be interested to follow your build...

Cheers,

Al

PS: mods, sorry, uploaded wrong data sheet. Please remove as I don't seem to be able to.