|
|
|
|
|||||||
| Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
 |
|
|
Thread Tools |
26th Aug 2020, 2:22 pm
|
#21 |
|
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,870
|
Re: Codar AT5 TX
You can getta lotta volts out of a carbon microphone, competing with crystal microphones.
Otherwise you need some amplification. But the carbon mike still needs DC power and the quality is not good. Used to be common in simple AM transmitters. Davi
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
|
|
26th Aug 2020, 5:09 pm
|
#22 |
|
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
|
Re: Codar AT5 TX
Crystal mics were no good in the car, a brief encounter with some sunshine would ruin them. The ideal mic for the AT5 I found to be the Shure 201 ceramic which seemed unaffected by heat yet had high impedance for the valve modulator. They do come up from time to time on that err popular Internet auction site.
__________________
Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way! 
|
|
|
31st Aug 2020, 5:33 pm
|
#23 |
|
Pentode
Join Date: Nov 2018
Location: Freckleton, Lancashire, UK.
Posts: 232
|
Re: Codar AT5 TX
As it happens just 'won' a shure 201 on said site for my AT5 / DX100 homebrew tx.
It'll be interesting to hear how is sounds compared to the eletret mic I'm using at present.
__________________
Building and tinkering for over 50 years, from 807's to digital amateur TV. |
|
|
|
31st Aug 2020, 6:35 pm
|
#24 |
|
Nonode
Join Date: Mar 2005
Location: Nuneaton, Warwickshire, UK.
Posts: 2,039
|
Re: Codar AT5 TX
DX100 homebrew. Is that a clone of the Heathkit one?
Love to see that Aub
__________________
Life's a long song, but the tune ends too soon for us all. |
|
|
|
31st Aug 2020, 6:54 pm
|
#25 |
|
Pentode
Join Date: Nov 2018
Location: Freckleton, Lancashire, UK.
Posts: 232
|
Re: Codar AT5 TX
I started of wanting to build an AT5 with a bit more punch and to cover 60mtrs as well as 160 and 80 mtrs - so the project evolved into an AT5 on steroids ultimately using a pair of KT88's, Woden UM2 mod tranny and a pair of 6146's in the final.
The design was a hybrid of a RSGB article mid 60's combined with a DX100 - trying to take the best bits from both of them. If you search for some of my earlier posts you'll see photo's of it. Here's one such thread https://www.vintage-radio.net/forum/...d.php?t=152370 and another https://www.vintage-radio.net/forum/...ight=g4wim_tim On air reports have been good but always thought it could benefit from an old style crystal mic - time will tell ! edit - apologies for thread drift off topic.
__________________
Building and tinkering for over 50 years, from 807's to digital amateur TV. Last edited by g4wim_tim; 31st Aug 2020 at 7:10 pm. |
|
|
|
31st Aug 2020, 8:59 pm
|
#26 |
|
Nonode
Join Date: Mar 2005
Location: Nuneaton, Warwickshire, UK.
Posts: 2,039
|
Re: Codar AT5 TX
Thanks for that. It looks great. I'll have to come on 3.615 more often with my homebrew.
73 Aub G4KQL
__________________
Life's a long song, but the tune ends too soon for us all. |
|
|
|
20th Feb 2021, 10:22 pm
|
#27 |
|
Triode
Join Date: May 2016
Location: Phimai, Thailand.
Posts: 49
|
Re: Codar AT5 TX
Hi all. Been reading about you microphone problems. I was wondering if an old insert from a old type of telephone would work?
|
|
|
|
20th Feb 2021, 11:11 pm
|
#28 |
|
Heptode
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 693
|
Re: Codar AT5 TX
Old telephones used a carbon microphone (variable resistance). You'll need to supply a couple of volts to pass some current through it. If you pass this through the low impedance primary of a step-up transformer you'll get plenty of audio on the secondary.
__________________
Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm |
|
|
