Re: [AMRadio] DX 60 mods
Thanks to all for the links and other great information. Paul, W9AC - Original Message - From: "Brian - KF5CCN" To: "Discussion of AM Radio in the Amateur Service" Sent: Saturday, July 03, 2010 2:41 AM Subject: Re: [AMRadio] DX 60 mods Here are links to the mods. I hope this is acceptable on the list. http://www.amwindow.org/tech/htm/wc3kmods.htm http://www.amwindow.org/tech/htm/dx60aud.htm 73 Brian Email: kf5...@arrl.net Web site: KF5CCN.COM --- On Sat, 7/3/10, rbethman wrote: From: rbethman Subject: Re: [AMRadio] DX 60 mods To: "Discussion of AM Radio in the Amateur Service" Date: Saturday, July 3, 2010, 12:04 AM Paul, Some are, some aren't and were published in Electric Radio. Then there is one that never made it to publishing due to Bill's sudden departure from this life. I sent out Links to the schematic earlier. While NOT well documented, Most savvy hams can work their way through. Let me know what you are looking for. The audio mods are VERY simple and easy to do. They expand the audio width by replacing a couple of caps. Bob - N0DGN On 7/2/2010 9:35 PM, Paul Christensen wrote: > Are the W3CK mods published on the web? Tnx! > > Paul, W9AC > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] DX 60 mods
Are the W3CK mods published on the web? Tnx! Paul, W9AC - Original Message - From: To: Sent: Friday, July 02, 2010 6:52 PM Subject: Re: [AMRadio] DX 60 mods >I have a DX-60 with the W3CK mods. It's AMAZING how many UNSOLICITED > AWESOME AUDIO reports I receive. People simply are sometimes in awe > that I am on a DX-60 (with the help of either an SB-200 or a Henry > 2K4). These are usually more seasoned AMers too. These mods are not > difficult and are very effective. The stock DX-60 is not bad at all > however. As for worrying about holes... well... there are a LOT of > DX-60's still out there. If you have a perfect example, then maybe you > should leave it alone. My radio is not a museum shelf piece but a > working transmitter. > > The over modulation indicator works spot on. When I see it flash more > than just a very dim red on peak audio, I can be assured I am over > driving the audio. A glance at the envelop on the scope confirms > flat-lining on the negative peaks. It is very accurate. > > The carrier level adjustment is something I'm not sure I could live > without now. It has become part of my tuning process. You see when > you adjust it, you have to touch up the audio level and sometimes the > loading and tuning to get everything "balanced". This ability is VERY > handy when driving a linear amplifier. It's sort of difficult to > explain but looking at a scope during tune up will clear that up. > > Bill also published a hint about the accessing the audio gain pot > without taking the chassis cover off. I use a wooden "ka-bob" skewer > bought in a pack of them from Wally-world (aka Walmart). They cost > less than a couple bucks. I whittled one end into the shape of a > flat-blade screwdriver. Looking down from the top ventilation holes, > you can see the audio gain pot. The hole directly above it becomes the > access with this long wooden "screwdriver". I just leave it in place > with a half inch handle. Works great. > > Anyone wanna try some 40 meter AM tonight? > > 73, John KX5JT > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] WTB - MURCH UT-2000A
> then re-wire it. I sure would. To a reversible "L" for use with coax lines -- or a balanced version of the L for open lines. With the classic C-L-C "T" design, multiple panel control settings can create an illusion of a low-loss transformation (unless output C is always maximized for the given load). The T is capable of reasonably low loss when the L and C components have a Q > 200 and the output C has > 3000-5000 pF of maximum capacitance where the connection point to the line is under 25-ohms. Myself, I cannot imagine using common wire antennas where the feedline Z at any point on the transmission line is less than 50-ohms. That almost always indicates an electrically short and inefficient antenna unless extraordinary measures are taken at the tuner and antenna to minimize system loss. Most off-the-shelf T tuners suffer great losses with low operating Z. Unless its for mobile use, I really do not want to use antennas that are much less than a physical 1/2-wave at the lowest operating frequency. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Broadcast stuff
>I looked it up, less then 2000 people work for the FCC. > The number has been going down for a while.Most seem to deal with legal > issues... A sprinkling of good news may be on the horizon: Two Congressional bills are being introduced, each termed the "FCC Commissioners' Technical Resource Enhancement Act." If one of the bills is passed, the Act will allow each Commissioner the opportunity to appoint an electrical engineer or computer scientist to liaise between the Commission leadership and OET. This is just the beginning of something long overdue at the Commission: the re-appointment of real engineers to facilitate engineering matters rather than a cadre of attorneys who generally choose easily-attained baccalaureate degrees in political science rather than pursue tough degrees in engineering and/or the sciences. I am an attorney, electrical engineer, and computer science major, so my biases against my primary profession are justified. > My company has stopped the fios builds and will likely switch to wireless. > You can get something like 340Mbps over wireless now. > That is a lot of bandwidth, with almost no infrastructure, no cables on > poles, no fiber, no high power broadcasting. The inevitable will slowly occur over time. The current broadband wire-line models are no longer cost-efficient to deploy and it makes little sense to simultaneously distribute 500+ digitally encoded video signals to each household when any household likely will not be watching more than a couple programs at any given moment. Narrow-casted wireless on micro-networks will eventually rule the content and communications world. The Achilles heel in the world of today's AM/FM/TV broadcasting environment is the lack of an interactive back-channel from the consumer to the station -- except through alternate media like the web -- and that just drives people away from the core broadcasting medium. Broadcasting needs its own interactive service and that will come when all the high-power RF is shut down and content streams through robust wireless networks. Content delivery has always been, and will continue to be "king," only the delivery method will change. I rarely have a liberalism moment, but this is an area where I strongly believe the federal government could/should step up to the plate and subsidize the entire cost a national broadband plan -- to an even greater extent than recently announced by the FCC earlier this week. Looking at the big picture, deployment and maintenance of a national wide-bandwidth wireless network is inexpensive to the government when you compare that cost against pre-existing retirement entitlements for the nation's largest employer, national health care benefits, and the national defense budget. Turn it over to private enterprise, let it compete against the existing wire-line services, and let the laws of "survival of the fittest" take over. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] FCC Non-cooperation (was ILLEGAL STUFF ON E BAY)
> Still, the intent of Part 15 is to protect licensed users from > interference from unlicensed devices, and the best option we have to > enforce current regulations (or potentially get better ones) is to > continue to elevate our concerns to the FCC and those who oversee the > agency. > > 73, Bob W9RAN Excellent advise, Bob. Part 15 needs to get current with the times. As more consumers replace their household appliances with models that incorporate RFI/EMI emitting technology, the problem will only become worse. The certification section was last re-written at time when nearly all of our major household appliances did not contain SMPS and microprocessors. Today, household "appliances" are exempt from Part 15 certification and problems associated with these unintentional radiators are dealt with after they generate interference to licensed services. The FCC could help itself in this matter with a rule change that includes appliances in the certification requirement. A bit of time spent on a rule change would pay great dividends in reducing their time spent on the enforcement effort. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] AM IARU Region 2 Bandplan
> "No place in Part 97 is the bandwidth for eater SSB or AM defined." Section 97.307(a) is the closest regulation we have pertaining occupied bandwidth in the American amateur service. However, some folks have argued that Sections 2.201 and 2.202 apply to the Part 97 service since Section 97.307(a) states: "No amateur station transmission shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice." Then, Section 2.202 defines "necessary bandwidth" and "occupied bandwidth" based on class of service. http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr2.201.htm http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr2.202.htm Reading Sections 2.201-2.202 together, the FCC has already incorporated much of the ITU's bandwidth and emission designators from Appendix 1 of its bandwidth recommendations. http://life.itu.ch/radioclub/rr/ap01.htm To the best of my knowledge, the FCC has never formally relied upon Sections 2.201-2.202 when addressing bandwidth concerns in the Part 97 service. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] QRM fron Neighbor's Security System
> "Years ago my young son bought one of those scooters with his own > hard-earned money..." Steve, The switch-mode chargers used for scooters are notoriously noisy. I had a similar issue with the neighbor to the side of me. These supplies offer little or no common-mode filtering between the switcher circuit and the AC line. In my own home, several SMPS have caused interference. I have been replacing SMPS types with used, industrial linear supplies (e.g., Lambda, PowerOne, etc.) Many SMPS designs are fine and produce no interference. The most problematic chargers seem to be imported from Asia and/or are imbedded into our household appliances where they are exempt from Part 15 certification. Part 15 requires an entire re-write since the proliferation of microprocessors and SMPS devices in common household appliances over the past decade. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] frequency sweeper
> Hi Paul: that seems to match with the interval I am hearing here between > the > two sweeps then the long interval, but, why do they do the wide freqencey > range, if that is what I am hearing. There's an IEEE paper that discusses the methodology although I've not read it. > is it a pulsed signal? That would take further analysis of the sweep. > I did not know that till looking at it, as it sounded clean as it swept > through wherever I > was listening. if so how can they legally transmitt on that entire freq > range? National security under DHS. I imagine they can, and will, do whatever they want Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] frequency sweeper
For those of you with Google Earth, the ROTHR transmitter Texas site can be seen here: http://tinyurl.com/yb7qcdo And the companion receive site: http://tinyurl.com/yeq5edl Each ROTHR transmitter site has a companion receive site located nearby. Presumably the receive sites are used to monitor the alternate transmit sites with data gathered and computed across all three receivers to display probabilities of illicit narcotics activity (and anything else DHS does with the information). By the way, the sweep intervals today are at 12 minutes. If you're in the Southeast US, listen to a clear spot on the 40m CW potion at these times: 1:13:00 PM Site 1 1:13:20 PM Site 2 1:25:00 PM Site 1 1:25:20 PM Site 2 1:37:00 PM Site 1 1:37:20 PM Site 2 1:49:00 PM Site 1 1:49:20 PM Site 2 All times ET. Site 1 is very strong here today, Site 2 is weak. I cannot hear Site 3 today. Paul, W9AC Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] frequency sweeper
> Apparently NOT an OTH radar, if it sweeps so > slowly. The 18 minute sweeps are coming from this ROTHR system. Each of the three sites can be heard, all with different signal strength depending on your location relative to their transmitters. The 18-minute cycle is not synchronized across all three transmitters. For example, you may hear Virginia at the top of the hour, next followed by PR 45 seconds later, then followed by Texas perhaps 15 seconds later. Once can record the signal strength from each of the sweeps then count 18 minutes and if propagation has not substantially changed, they are easily identified. What I need is an 18-minute look ahead timer that automatically engages my 20 dB attenuator for a split second! Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] frequency sweeper
> "If it sweep perhaps a hundred kc at a time, and at a rate of perhaps 10 sweeps per second, then I would bet on OTH radar..." More than likely, the sweeps you're referring to are created by this monster... http://www.raytheon.com/capabilities/rtnwcm/groups/public/documents/content/rtn_bus_ids_prod_rothr_pdf.pdf Every 18 minutes, the Department of Homeland Security is sweeping the ionosphere from three locations as it triangulates illicit drug activity involving ships and aircraft. Here in the Southeast, we experience +40dB/S9 sweeps starting around 6MHz up through roughly15 MHz from each of three synchronized ROTHR sites located in Virginia, Texas, and Puerto Rico. The sweeps are constant and always upward moving in frequency. I have developed an almost Pavlovian fear of the blast every 18 minutes on 40 meters. If one has a pan adapter connected to their receiver, the sweep can be seen marching across the screen. The next time anyone thinks someone is simply checking the SWR of their antenna by sweeping their transmitter's VFO, the interference just may be coming from DHS. The 18 minute interval is a dead giveaway. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
> Not sure that Euro or Phoenix connectors were around (or at least readily > available) when these beasties were built. Strictly 1970's low tech. Bill AD5OL They were around in 1995 -- the last time I had seen a Logitek Mixer installed. Other options existed then as well, including 6, 9, 12, and 15-pin Molex to keep wiring density manageable. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
> Amen to Steve's comments on Logitek. They run 120V. from the back panel to > the power switch on the front panel on a piece of Belden 8451 shieded pair > audio cable bundled in with the microphone lines from the back panel > connectors. Shall we say less than "best engineering practices". And... Consideration to rack placement is critical. If access to the Logitek's top cover is needed for maintenance and its obstructed, it means removing every single wire to an array of screw-down barrier strips. A better solution for Logitek would have been to design a back-plane using miniature Euro-Block connectors so that groups of plugs can be unplugged from a mating barrier jack. Need to remove the mixer from the rack? No problem. Just unplug a few connectors and reconnect when maintenance is complete. For most equipment, removing a few wires is not problematic. But when you consider the number of possible connections on the Logitek back-plane, removing every wire can be a nightmare. Fortunately for amateur radio purposes, not too many of us need a lot of inputs -- unlike typical remote broadcast demands. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
> found a better rackmount mixer to replace it yet. I'd like to get a > Pacific Recorders NewsMixer but haven't found one priced cheap enough > for my budget. I would check with Mooretronix. Although they primarily service PR&E product, from time-to-time they also have reconditioned consoles available for purchase. Not too many of the NewsMixers exist. When production was running, they were primarily sold to large group owners. Few medium and small-market stations could afford them. http://www.mooretronix.com/ Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
Jim, The LTSpice plot shows why the stock Astatic 2-stage pre-amp with its ~ 470K-ohm input Z does little to extend low-end response. The model also likely assumes a perfect C in series with the source. After testing several D-104 cartridges of different vintage, I've come to the conclusion that distributed resistance appears across the crystal, thereby limiting any additional benefit of an extraordinarily high inout Z beyond 10 meg-ohm. Although not shown through the model diminishing returns hits pretty fast just above 5 megohm. I've not seen any element produce a reasonably flat response below ~ 50 Hz. Still, as long as the target is about 70 Hz to hit the lowest of vocal fundamentals, there's no reason to strive for anything better unless one relishes the sound of room rumble which in turn also unnecessarily raises RF duty cycle. Paul, W9AC - Original Message - From: "Jim Tonne" To: "Discussion of AM Radio in the Amateur Service" Sent: Tuesday, September 22, 2009 11:07 AM Subject: Re: [AMRadio] Microphone recomendation > > I have been lurking here and reading the discussion > which seems to me to have reduced itself down to a > kind of "my daddy is better than your daddy" kind of > thing. > > The person who said the D104 microphone could be > thought of as a voltage generator in series with a > 500 pF capacitor hit the nail on the head! Exactly > correct (although I thought it might be a *slightly* > higher capacitance value). > > I have spent a few minutes with LTspice and made > a plot which clearly shows what happens when you > change the value of the load on the D104 microphone. > With a 10 megohm load the -3 dB point will be right > at 30 Hz. > > Please, fellows, take a quick peek at this plot: > http://tonnesoftware.com/appnotes/D104loadTest.gif > > The bottom line of this note is that going higher than > 10 megohms for a load is nonsense. Pure nonsense. > > - Jim W4ENE > > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Microphone recomendation
> pair of high-mu triodes in a push-pull mic preamp. That way, each tube > can > have its own 10 meg grid leak to allow for a 20 megohm load on the xtal. It's possible to duplicate a similar circuit using an FET differential amplifier with dual FETs in a single package (e.g., 2SJ109), or a JFET-input instrumentation amp (e.g., LT1102). Both would perform best when using a bi-polar supply to economize on parts count and avoid having to use half-rail biasing technique. In each case, input Z is 2x the single-ended amp for a total of 22 meg-ohm. The circuit could be installed in the D-104 mic head, with shielded twisted-pair running to a balanced-input speech amp. Seems like there are other factors that limit the practical input Z to ~10 megohm for a crystal cartridge. The source Z and slight shunt resistance internal to the crystal cartridge may be the limiting factor. I've used a series input R of 10-meg in front of my single JFET's gate and the response is pretty much limited to about 50 Hz with or without the added R -- with the only noticeable difference being lower output level and increased noise. With the first fundamental of the deepest male voice being greater than 70 Hz, it's kinda' hard to justify a response that extends any lower for any form of voice communication, including AM and ESSB. Anything lower than 70 Hz unnecessarily increases power duty cycle and produces other unwanted artifacts like room rumble and deep breathing sounds. Paul, W9AC __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
