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Re: OT
Vince Vielhaber
If you were using an email client instead of going to the site, you'd see their email address. You'd also be able to quote some of what you're responding to!
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Vince. On 08/29/2017 06:39 PM, Dexter N Muir wrote:
Sorry, address shows in composition window but not beyond :( --
Michigan VHF Corp. |
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OT
I've just had a very pleasant off-topic interaction with Keith VE7GDH, and there's no way to take it off-list. Can we please have facebook-style ability to "pm" (private-message) - right-click-on-name option - and, why not? - emoticons? Probably a major overhaul to html - with associated security issues? Me, I work better with email, so my address shows.
73 de ZL2DEX |
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Re: BITX QSO Night, Sunday, August 27, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
Dex ZL2DEX wrote...
??? How would one educate an antenna? The word would be "taut"I taught it to be tight? hi! Yeah, that was a typo. It should have been taut... or tight. Ummm... was that a glass of wine in one of the photos? 8-) Perhaps I can blame that! -- 73 Keith VE7GDH |
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Re: Heat Sink
Jack Purdum
No more shark fin :>( Hello iPhone! :>) Jack, W8TEE From: chris gress <Chrisg0wfh@...> To: [email protected] Sent: Tuesday, August 29, 2017 1:52 PM Subject: Re: [BITX20] Heat Sink I use a large heat sink my pa has never got warm chris On 29 Aug 2017 17:49, "Keith VE7GDH" <ve7gdh@...> wrote: Here's the heat sink I'm using and the stock one. Except for a test, I'll probably always run it on 12V. The IRF510 has never been warm to touch when I've been using it, but the replacement heat sink has twice the area and three times the thermal mass. |
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Re: BITX QSO Night, Comments
philip yates
Couple of points, yes the Bitx is quieter, have heard dx that my FT1000 struggles with, which was a great surprise.? Other note.... Us lot in Europe cannot go above 7.2mhz and the broadcast stations kill most of the amateur tx. Sunday is not the best either, have loads more time on a Saturday, other half lets me stay up later. Lol.. Phil - G7BZD On Tue, Aug 29, 2017 at 8:28 PM, Dexter N Muir <dexy@...> wrote: In speech, the ConSonanTS / sibilants tend to carry the 'intelligence' while the VOwels carry the VOlume. Here in NZ it's usually "calling Mr. Harlow" - "Haaaaaalo". Any vowel should do the trick, though Ah and Oh seem to work best. Maybe the aspirant 'h' helps too, and why laughter has it- Ha, Hi, Hee ... :) I really do miss emoticons here, though I see Baruch Atta manages to get one through - what keystrokes do that? |
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Re: BITX QSO Night, Comments
In speech, the ConSonanTS / sibilants tend to carry the 'intelligence' while the VOwels carry the VOlume. Here in NZ it's usually "calling Mr. Harlow" - "Haaaaaalo". Any vowel should do the trick, though Ah and Oh seem to work best. Maybe the aspirant 'h' helps too, and why laughter has it- Ha, Hi, Hee ... :) I really do miss emoticons here, though I see Baruch Atta manages to get one through - what keystrokes do that?
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Re: Automatic RF Attenuation Mod for Bitx40
Jim first referenced that other circuitry in this post: ? ?/g/BITX20/message/31875
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But yes, I agree, I'd expect these parts to work ok at least down to 3.5mhz,? and I don't have much interest in going any lower. On Tue, Aug 29, 2017 at 12:04 pm, Henning Weddig wrote:
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Re: Automatic RF Attenuation Mod for Bitx40
Datasheet of the BA479G says the "minority carrier lifetime" is typically 4 uS.
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That's the average time it takes for the hole or electron to get swallowed up. You would have to take it down to 1/(2*4uS) = 125 khz before you had 4 uS between peak forward current and peak reverse current, at which point I assume the reverse current would diminish by about half. ? Perhaps AM broadcast signals in the 550-1700 mhz range would be distorted some, creating harmonics that add to the noise at HF. But if the Bitx40 receiver sounds as well on weak signals with this attenuator inline as it does without the attenuator, then I'd think the BA479G is plenty good enough. I could be wrong about any of the above, PIN diodes are not ?something I claim to know much about. I had previously said: "we can probably do without ?C4 L2 D1 C2 C6 C7 and just drive L1 from about 4 volts Those parts seem to be there to rectify incoming RF and use that rectified signal to further attenuate the signal, providing some local AGC action." If that is true, then it is a feature we don't want here. We don't want an out of band signal such as a strong local AM broadcaster to throttle back our 40m signals.? Jerry On Tue, Aug 29, 2017 at 11:10 am, <jpkellyburbank@...> wrote:
My first choice for the Pin diode was the?BA389, but I could only find it at??where they have a 30 Euro minimum order. ?I also tried the MA27B from RF parts and it worked as well as the BA479G, so I assumed the 10 Mhz minimum in the specification is not a hard limit. ?I also have some MI105 pin diodes coming from Asia that I will be trying, but so far the pin diode choice does not seem to be critical. |
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Re: Automatic RF Attenuation Mod for Bitx40
开云体育Jim, for the PIN diode to work properly as a variable resistor, and
not rectify the RF the so called carrier lifetime n(minority
carriers ??)? is an important factor. Jerry Gaffke proposed another circuitry of the same topology but a different diode, i.e. the BA595 from Infineon. From the data sheet the carrier lifetime is specified 1600 ns 1/1600 ns= 625 kHz, so this diode is really suited for attenuation i.e. acting as a resistor for frequencies above 1 MHz. Opamp: if You put a resistor (about 100 ohms or so) in series
with the output of the opamp and then the cap tor ground the
possibility of an oscillating opamp? will be gone. From my simulations the BITX40 has one big drawback: the high gain AF preamp (LTSPICE XVII tells me 46 dB gain) , so every AF AGC after this amp will limit the dynamic range, as the AF preamp? is the "weak" point. Pl?ease have a look on my level diagramme in the DK5LV folder. 73 Henning DK5LV Am 29.08.2017 um 20:10 schrieb
jpkellyburbank@...:
Hello Henning, |
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Re: Automatic RF Attenuation Mod for Bitx40
Hello Henning,
My first choice for the Pin diode was the?BA389, but I could only find it at??where they have a 30 Euro minimum order. ?I also tried the MA27B from RF parts and it worked as well as the BA479G, so I assumed the 10 Mhz minimum in the specification is not a hard limit. ?I also have some MI105 pin diodes coming from Asia that I will be trying, but so far the pin diode choice does not seem to be critical. The op amp stage that has the capacitor on the output is functioning as a voltage follower. ?I added the cap as a precaution for any RF problems, but I suppose it is not actually necessary. Anyway, I have built and tested and am not noticing any oscillations. Jim/ND6P |
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Re: Heat Sink
chris gress
I use a large heat sink my pa has never got warm chris On 29 Aug 2017 17:49, "Keith VE7GDH" <ve7gdh@...> wrote: Here's the heat sink I'm using and the stock one. Except for a test, I'll probably always run it on 12V. The IRF510 has never been warm to touch when I've been using it, but the replacement heat sink has twice the area and three times the thermal mass. |
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Re: BITX QSO Night, Comments
"And a number of us have noticed that the BitX is much quieter than a lot
of big rigs.? The BitX is certainly quieter than my Icom 718.? That's
amazing.? Does anyone have any theories on why this is?" Over the past years many have noticed how quiet the BITX design really is.? This? seems to be because each gain stage is designed for fairly low value of fixed gain instead of running at full gain.? This apparently causes the 2N3904 devices to generate less internal noise, thus the lower overall noise floor in the receiver.? It also helps that much of the receiver gain is in the audio section where BJT gain stages are usually quieter. ?? Arv _._ On Tue, Aug 29, 2017 at 10:28 AM, Baruch Atta <baruchatta@...> wrote:
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Re: BITX QSO Night, Comments
I often tune by 7.277 and listen, but do not make a call. I'll start making a few calls when I check the frequency rather than listen and pass on. I am also working on an antenna solution for west/southwest from my QTH. The goal is VK or ZL dx?which I am receiving already, but?can't make the contact.??It should make the west coast better from here as well.
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Re: BITX QSO Night, Comments
Baruch Atta
I read all the comments so let me add my own: The time of the net is as good as any other for me. ?7 PM local on Sunday. 7277 khz. Please if you have a contact going, and it is a BitX contact, please call for check ins or other break in stations after each "over".? Make it a habit.? Rag chews are ok on the frequency as long as they call for check ins every over.? I kinda cringe with the term "rag chew".? Can't we just say "chat"?? Have you ever chewed on a rag?? Yes? No? "Barefoot" (100 watt) rigs or other QRP rigs are welcome. ? I made the modification to swap the original frequency determining caps in the VFO with NP0 caps.? It made all the difference.? To find my exact frequency, I zero beat with my big rig. After a bit of warm-up the BitX is as steady as a (soft) rock.? And a number of us have noticed that the BitX is much quieter than a lot of big rigs.? The BitX is certainly quieter than my Icom 718.? That's amazing.? Does anyone have any theories on why this is? In fact, speaking of chats, chatting is good on this net, because it allows stations like myself to find the correct frequency.? Just don't talk for a long time each transmission, and call for check ins between every over.? I think that talking for a minute would be ideal.? Then give the other guy a chance.? It will come back to you soon.? After the BitX net/round robin, there is the 3905 Century Club net at 8:00 PM eastern.? I just checked in to the 3905 CCN with my BitX.? Perhaps you would like to also?? It is on 7.267,5 MHz. It is a directed net, so you have to take your turn to check in, and take your turn to call another station.? It is a lot of waiting, but you get to hear stations from all over, and pick the one you want to call on your turn.? We ALWAYS QSL. ? I find that speaking into the mic very strongly really helps particularly with the Bitx.? Me too. ??Me too. I have a power meter in my tuner, and I watch it as I talk.? I get the most power with the ol' BitX phrase "Heeellllooooooo", made famous by Ashhar.? Maybe instead of CQ we all could call "Helloooooooo"? ?? On Tue, Aug 29, 2017 at 11:37 AM, Karl Schwab via Groups.Io <ktschwab@...> wrote:
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73, Joe W3TTT |
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Re: MY BITX 40
Avijit VU3MVH wrote...
The rig is still in search of a cabinet...Now, that's a heat sink!!! Congratulations on getting your BITX40 on the air. I intended to fire mine up like yours to check it out, but ended up getting it mostly bolted into the cabinet before trying it out. I've only had to unbolt it once to change the PA which probably wasn't needed, but it will have to come out again to put a couple of diodes under the board to protect Q13. The front and back of the case slide out, so it's easy to get to the top of the board and the SMD parts. I'm not sure if we could ever make contact on 40M, but perhaps on 20M and up when propagation improves! -- 73 Keith VE7GDH |
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