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Bob Larkin, W7PUA, has built a new radio!

Ashhar Farhan All Messages By This Member #115857 Bob Larkon, W7PUA, is one of the three authors of the EMRFD. He has been a large influence over?the years, and I learnt a whole lot of RF and SDR stuff from him. He is a remarkable homebrewer and a very thorough and astute designer. He has desiged a very unusual radio, the Tiny Ten. Do read about it on It is a standalone IQ radio QRP radio with swappable filters for different bands powered by a Teensy. Unlike the under performing SDRs that we see around these days, it is a real thing with? a very thorough design and high performance. - f
Richard Spohn All Messages By This Member #115865 Verrrrry Interesting!? Any plans to market the Tiny Ten, either as a kit or assembled? toggle quoted message Show quoted text On Mon, Feb 24, 2025 at 6:59?PM Ashhar Farhan via <farhanbox=[email protected]> wrote: Bob Larkon, W7PUA, is one of the three authors of the EMRFD. He has been a large influence over?the years, and I learnt a whole lot of RF and SDR stuff from him. He is a remarkable homebrewer and a very thorough and astute designer. He has desiged a very unusual radio, the Tiny Ten. Do read about it on It is a standalone IQ radio QRP radio with swappable filters for different bands powered by a Teensy. Unlike the under performing SDRs that we see around these days, it is a real thing with? a very thorough design and high performance. - f
Ashhar Farhan All Messages By This Member #115866 Knowing Bob, he might just release the pcb layout. There so many jewels in there. Who can figure out how the antenna relay on the RF board works? Quickly! toggle quoted message Show quoted text On Tue, Feb 25, 2025, 6:35 PM Richard Spohn via <wb2gxm=[email protected]> wrote: Verrrrry Interesting!? Any plans to market the Tiny Ten, either as a kit or assembled? On Mon, Feb 24, 2025 at 6:59?PM Ashhar Farhan via <farhanbox=[email protected]> wrote: Bob Larkon, W7PUA, is one of the three authors of the EMRFD. He has been a large influence over?the years, and I learnt a whole lot of RF and SDR stuff from him. He is a remarkable homebrewer and a very thorough and astute designer. He has desiged a very unusual radio, the Tiny Ten. Do read about it on It is a standalone IQ radio QRP radio with swappable filters for different bands powered by a Teensy. Unlike the under performing SDRs that we see around these days, it is a real thing with? a very thorough design and high performance. - f
Kees T All Messages By This Member #115867 I hope Bob does release it. Pretty impressive function but the display could stand an upgrade to a real screen. Amazing how much expertise is available worldwide and gladly shared with others. It can only get better in the future. Not AI, but EI Expert Intelligence. ? 73 Kees K5BCQ
Gerald Sherman All Messages By This Member #115869 开云体育 AI is real stupidity!! Gerry Shermaan On 2025-02-25 15:52, Kees T via groups.io wrote: toggle quoted message Show quoted text I hope Bob does release it. Pretty impressive function but the display could stand an upgrade to a real screen. Amazing how much expertise is available worldwide and gladly shared with others. It can only get better in the future. Not AI, but EI Expert Intelligence. ? 73 Kees K5BCQ
Bruce MacKinnon KC1FSZ All Messages By This Member #115889 The NPN in the driver stage (BFU590GX) looks interesting. ? Bruce KC1FSZ ?
Ashhar Farhan All Messages By This Member #115890 Ok, about the relay first, You will realize that it is a latching relay with a single coil. So? 1. if there is no current through it, it stays in whichever state it is (on or off) 2. If you pump current in one direction through the coil it gets latched on. If you remove the current the relay continues to remain on. 3. If you pump the current in the other direction through the coil, the latch comes off, if you remove the current the relay continues to be off This kind of relay usually needs?an ability to swing voltage on both sides of the latch to?pass current in both directions.? In this genius work, There is a capacitor at one end of the relay (lets call that end of the latching coil as A). Let's imagine that the?capacitor is discharged and the other end of the coild?(Let's say B) is also low. Nothing happens. Next, the B end is pull high (like a regular relay). The capacitor being dischraged?allows the current to flow from B->A , latching the relay on. The capacitor eventually charges to the high voltage and no more current flows through the relay.? Now, when the B end is pulled down, the capacitor at A end of the relay coil discharges, reversing the current flow, turning the relay off, the current continues to flow until the capacitor is discharged, then no more current flows! About the driver amplifier, it provides 20 db gain without a trifilar transformer. This works even with the 2N2222 all the way to 14 MHz. Of course, the 2N2222 won't handle this large a current. We have used this in the zbitx. - f toggle quoted message Show quoted text On Thu, Feb 27, 2025, 7:42 AM Bruce MacKinnon KC1FSZ via <bruce=[email protected]> wrote: The NPN in the driver stage (BFU590GX) looks interesting. ? Bruce KC1FSZ ?
Gary Anderson All Messages By This Member #115900 For reference: Single coil latching relay application note: ? -Gary
Robert Campbell All Messages By This Member #115903 Ashar, Thank you for letting us know about this project from Bob.? It looks interesting. I first figured out how those latching relays work when looking at the Elecraft T1 antenna tuner schematics.? In that case, there were many relays, with one side of each coil going to an individual microcontroller pin and the other side of all the relays tied together, with a single capacitor to ground tied to that same point. It took me a little bit to figure out how it was able to turn certain relays on or off without affecting the others.? I don't know who originally came up with that method, but it was someone smarter than me. Here is that part of the schematic from the T1 manual: -- Rob Campbell? KG6HUM toggle quoted message Show quoted text On Wed, Feb 26, 2025, 18:30 Ashhar Farhan via <farhanbox=[email protected]> wrote: Ok, about the relay first, You will realize that it is a latching relay with a single coil. So? 1. if there is no current through it, it stays in whichever state it is (on or off) 2. If you pump current in one direction through the coil it gets latched on. If you remove the current the relay continues to remain on. 3. If you pump the current in the other direction through the coil, the latch comes off, if you remove the current the relay continues to be off This kind of relay usually needs?an ability to swing voltage on both sides of the latch to?pass current in both directions.? In this genius work, There is a capacitor at one end of the relay (lets call that end of the latching coil as A). Let's imagine that the?capacitor is discharged and the other end of the coild?(Let's say B) is also low. Nothing happens. Next, the B end is pull high (like a regular relay). The capacitor being dischraged?allows the current to flow from B->A , latching the relay on. The capacitor eventually charges to the high voltage and no more current flows through the relay.? Now, when the B end is pulled down, the capacitor at A end of the relay coil discharges, reversing the current flow, turning the relay off, the current continues to flow until the capacitor is discharged, then no more current flows! About the driver amplifier, it provides 20 db gain without a trifilar transformer. This works even with the 2N2222 all the way to 14 MHz. Of course, the 2N2222 won't handle this large a current. We have used this in the zbitx. - f On Thu, Feb 27, 2025, 7:42 AM Bruce MacKinnon KC1FSZ via <bruce=[email protected]> wrote: The NPN in the driver stage (BFU590GX) looks interesting. ? Bruce KC1FSZ ?

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