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Bazz4CQJ · 14th Aug 2020, 11:12 pm

John, I wonder if you are familar with George Smart's webpage https://www.george-smart.co.uk/projects/wellgood_loop/regarding his investigation of the Wellbrook antenna?

Comments made on his site are as follows;

The transistors used in the original design were ZTX327, and so this board is designed to fit those. These are now obsolete and are quite expensive to acquire from sources such as eBay. A ZTX653 has a matching pinout with suitable characteristics, and would be a direct drop-in replacement for the ZTX327. Preliminary tests were done with an MPSH10, but the pinout is different, and so require some tweaking to fit to the board. The original ZTX327 transistors had a hFE-min of 15. It is important not to have too high forward current gain (hFE) on the transistors, as this will disturb the correct biasing of the transistors. The pinouts are shown below. Dave GW3WCV writes in (see Feedback section below) to say that he had success with PN2222A devices, which improve the higher frequency performance, too. I have since been using PN2222 devices with improved results and it is pin-compatible with the ZTX327. The PN2222 is my preferred choice.

However, I don't recall whether or not George makes any comment about frequency coverage. It does seem to be the case that a lot of people investigating magllops are only interested in low frequency (MW/LW?) whereas I'm playing aroun on 80m (using 2N3866). A number of people have reported using either 2N5109 or 2N3866 successfully in the amp, but these physically larger transistors are a bit of a squeeze on that PCB. There was also some reason to think that some 5109's which were on sale online in the UK were bad, with gains of only ~40.

I'm beginning to loose track of how many threads there have been on the Forum on magloops this last ~3 years (5 or 6?). I wonder if it would be a good idea to have a single on-going thread?

B

14th Aug 2020, 11:12 pm	#15
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	Re: Lockdown Loop Aerials John, I wonder if you are familar with George Smart's webpage https://www.george-smart.co.uk/projects/wellgood_loop/regarding his investigation of the Wellbrook antenna? Comments made on his site are as follows; The transistors used in the original design were ZTX327, and so this board is designed to fit those. These are now obsolete and are quite expensive to acquire from sources such as eBay. A ZTX653 has a matching pinout with suitable characteristics, and would be a direct drop-in replacement for the ZTX327. Preliminary tests were done with an MPSH10, but the pinout is different, and so require some tweaking to fit to the board. The original ZTX327 transistors had a hFE-min of 15. It is important not to have too high forward current gain (hFE) on the transistors, as this will disturb the correct biasing of the transistors. The pinouts are shown below. Dave GW3WCV writes in (see Feedback section below) to say that he had success with PN2222A devices, which improve the higher frequency performance, too. I have since been using PN2222 devices with improved results and it is pin-compatible with the ZTX327. The PN2222 is my preferred choice. However, I don't recall whether or not George makes any comment about frequency coverage. It does seem to be the case that a lot of people investigating magllops are only interested in low frequency (MW/LW?) whereas I'm playing aroun on 80m (using 2N3866). A number of people have reported using either 2N5109 or 2N3866 successfully in the amp, but these physically larger transistors are a bit of a squeeze on that PCB. There was also some reason to think that some 5109's which were on sale online in the UK were bad, with gains of only ~40. I'm beginning to loose track of how many threads there have been on the Forum on magloops this last ~3 years (5 or 6?). I wonder if it would be a good idea to have a single on-going thread? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.