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Feel free to add information to the wiki or make edits as needed. Please respect the work of others by adding your own content rather than editing or removing someone else's content unless doing things like updating URL's etc.?
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Re: Requested Files
Hey K!
...yeah that's what I was thinking...but no one seems to be answering there. I contacted Chuck Adams (K7qo) about them (since he helped build them) and he said he didn't have any of those things. He pointed me to "the groups.io site" -- Not sure where he was thinking but there weren't any files or boards for sale that I could see.? Thanks for the link...but I don't see any files listed there and no one's monitoring membership as far as I can tell.? still searching...? Tom |
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Re: NC-40 Multiband??
Bob Macklin
¿ªÔÆÌåÓýWhat is wrong with the 9850 if you use the square wave outputs?
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Bob Macklin
K5MYJ Seattle, Wa. "Real Radios Glow In The Dark"
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Re: Requested Files
You need to get these files from the old arp-tech group:?
/g/qrp-tech/files/Winter%202018%20Project%20%231%20--%20%20NorCal40A%20qrp-tech%20PCB de Karl Heinz - K5KHK |
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Re: NC-40 Multiband??
FYI the K1 and K2 stuck with relays as diodes not done really well can
really hurt?the receiver overload capability.? It shows as back when the K2 was top of Bob Sherwoods list for RX performance.? Simple done well. Also diode switching at power is harder to get right, even a few watts. Antenna switching for QSK however can be done but with great care. The yabut is that the RX agc(if used) needs to recover fast enough to work. Allison |
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Re: NC-40 Multiband??
There is only one reason why DDS can't be used, you need a good one
not the 9850. Otherwise yes a DDS would replace the VFO and mixer plus the LO filter. However use the si5351, generally more available, cheaper and good from a few khz to over 100mhz.? You still need the Arduino and LCC and a rotary encoder.? Basically the same scheme as Raduino (used for the uBitx). FYI the square wave output from the 5351 is compatible with DBMs with an attenuator and 602/612 with a attenuator (need only 300mV PP? and the 5351 is about 3V PP) The beauty of the Arduino and si5351 is a computer can tell it what frequency and all.? the volume and otehr controls are sill analog but? there are ways... Allison |
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Re: DDS VFO!
They have one thing going for them, very pow power consumption.
I started playing with DC receiver back in the 70s.? Looked promising but they were not all that.? Like regens, the are useful. the HW9 was the solid state version of HW16,? a superhet RX with filter and decent keying.? Also still low power. With DBMs or SA612 added to the recognition that ladder filters are relatively easy and huge IF gain is not needed superhets became simpler. I've applied those ideas to tube based RX and ended up with a good receiver in 3 tubes. Those being? 6AU8 mixer oscillator, ladder filter, 6BE6 product detector, 6GW8 audio preamp and power amp.? Other choices are also possible.? The 6BE6 or 6AR8 being close to a vacuum tube version of the SA612 for mixers. Allison |
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Re: DDS VFO!
Bob Macklin
¿ªÔÆÌåÓýI know about the potential problems of DC receivers. That's why I have always avoided them.
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I know the HW-8 was better than the HW-7. But a lot of both were sold.
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Bob Macklin
K5MYJ Seattle, Wa. "Real Radios Glow In The Dark"
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Re: NC-40 Multiband??
Bob Macklin
¿ªÔÆÌåÓýYes,
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I went back and looked at the manuals on the Sierra, K1, and K2.
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They all use the? same scheme where they mix the VFO with a crystal and use that product for the Rx (Tx) LO.
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The crystal frequencies are the same on all three designs.
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Why can't a DDS be used?
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The DDS can be programmed for the mixed frequency and used directly.
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Do you want single band or multiband? For multiband you can use a off board switched bandpass filters similar to the way Burdick did it.
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But I would look at PIN diode switching rather than relay switching.
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Or you can do it with the analog VFO and crystal mixer the way Burdick did it.
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My goal is to have a transceiver that I can run from a computer.
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I'm 85 years old and I have problems with my hands and hearing.
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But I still like radios.
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I hope I live to 90 so I can possibly see better propagation again.
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Bob Macklin
K5MYJ Seattle, Wa. "Real Radios Glow In The Dark"
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Re: DDS VFO!
NC-40 has a crystal filter and that would be a good RX in its own.
Attached the receiver schematic.? Its roughly the same as K1 and 1W (kitsandparts.com). Generally much better than DC rx. Direct conversion the best of the lot are the Tentec century 21 and 22. The HW8 was the best in the heath line. the problem is the Image frequency can be hear so if you have a CW signal tuned in right there can be another guy on the other side your can hear. The other issue (operator training) is if you tun in a station on the wrong side you can call him till your worn out as he is not listening there.? The upside to DC RX is with a good audio filter the receiver can sound very good. Allison |
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Re: NC-40 Multiband??
OK ,
First the Norcal sierra is single conversion with a 4.915mhz IF. See schematic! There is no 8mhz IF or front end.? It is able to band switch using plug in boards. That could be relay switched but its a lot of relays (looks like 6 per band for clean switching) Dialing it in for 8mhz is doable and maybe easier for a monoband chassis like NC40 but less trivial for the neophyte builder.? As the basic chasis carries the transmitter and the traansverter (that's whats being proposed) need to be interposed between the Tx mixer and the actual transmitt power chain.? ?Conceptually easy much harder to do in practice. It is unique a its one of the few ith VFO and usis a convershon scheme to hit? other bands as needed.? The Elecraft K1 is very close in design.? That means same crystals. For both you need band pass filters, low pass filters, and a filter in the VFO conversion for the band choice. Norcal those are PMO filter, with matching crystal, TX BPF RX BPF TX LPF. For the NC-40 its about the same game save for you really need a digital VFO and not 9850 based though the Si5351 does work well for that.? The bigger issue the NC40 was a monoband radio from the start and lacks easy change points for multiband. For either: The 4.915 IF you need four matched in frequency to get a good CW filter. A frequency counter and a simple oscillator circuit works for that.? ?kitsandparts.com can supply them matched for $1.50 each. ? ?The Norcal Sierra needs 7 total.? 5 are in the filters? rest are bfo/Tx offset ? ?The NC40 requires 6.? ?4 are in the filters? rest are bfo/Tx offset Allison |
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Re: NC-40 Multiband??
Bob Macklin
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NC-40 Multiband??
Bob Macklin
Think about this.
There were some comments in the origianl NC-40 manual about modifcations for use on other bands. The NorCal Sierra and Elecraft K1, K2 use a 8MHz high IF. The 8MHz signal is converted down to 4.915 and the LO IF looks much like the NC-40. You could modify the NC-40 to transmit and receive on 8.000:8.500. The you can build a frontend converter like the Sierra and K1. convert the regular ham bands to 8MHz. (revese for transmitting. You can use the same crystals used in the Sierra and K1. They are all available at Mouser or DigiKey. I need to build a setup to select matched 4.915MHz crystals for the IF filters. Maybe an Arduino project? Bob Macklin K5MYJ Seattle, Wa. "Real Radios Glow In The Dark" |
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Re: Group Introduction: If you're going to post on the group, reply here!
I mostly lurk unless something of personal interest comes up (like adding a DDS VFO to a NC40A!) because my technical knowledge is pretty low. But I do learn a lot from the folks to regularly post so I am glad that Chuck's group will live on in a way. Sad to see him shut it down but nothing lasts forever in the cold November rain.
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