Some Good Murania News


Philip Karras <ke3fl@...>
 

OK, some good news. From information from Ev Catlin N5MZX I was wondering if the loop was the problem. So I pushed it flat to the board closer to the tuning cap and I was able to receive WBAL. WBAL is a very strong AM station from Baltimore about 20 miles away from me at 1090. The Murania receives it from 700 to 900 on the dial depending on the antenna (I'll explain that in a bit) it is stronger either near 700 or near 900.

By antenna I mean that if I place the ferrite antenna close to a long wire, my coax going to a 2m+70cm J-Pole, WBAL comes in much stronger and closer to 900 than to 700. If I use only the built in ferrite antenna then WBAL is louder closer to 700 than 900.

So, I'm assuming a long wire antenna would also help.

Question, since WBAL is coming in between 700 and 900 when it should be in the 1090 range does this mean I placed one too many or one too few loops on the ferrite?

Hey I found this: https://goodcalculators.com/resonant-frequency-calculator/

This shows if the cap is at 100 pf and the inductor at 350 µH the Resonant freq (Rf) is ~850 KHz, if the inductor is 300 µH then the Rf ~ 918 KHz so if my Rf is too low on the dial it means I need less inductance and that means fewer loops around the ferrite. Fewer loops == lower inductance.

73 de KE3FL,
Phil
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Curt
 

Phil

These receivers using regeneration have different physics. You should not need more antenna, a loopstick will receive AM stations by itself over hundreds of miles at night.

Also better to have less coupling between the antenna and regeneration circuitry. Counter intuitive but true. Tuning is sharper with less signal coupled in, and the regeneration makes up for it. Patiently try less coupling. You want higher Q to get better selectivity.

My own AM regen is different, it uses a tube at 12 volts only on the plate. Like n3sb reports for his Murania, it pulls in dx at night. I also have a homebrew ozark patrol here, and a few other regens.

I did run across a blog discussing a modified murania, but get your stock radio working better with some adjustments.

Curt


Everett Catlin <everettcatlin@...>
 



On Friday, February 12, 2021, 3:37:48 PM UTC, Philip Karras via groups.io <ke3fl@...> wrote:


OK, some good news. From information from Ev Catlin N5MZX I was wondering if the loop was the problem. So I pushed it flat to the board closer to the tuning cap and I was able to receive WBAL. WBAL is a very strong AM station from Baltimore about 20 miles away from me at 1090. The Murania receives it from 700 to 900 on the dial depending on the antenna (I'll explain that in a bit) it is stronger either near 700 or near 900.

By antenna I mean that if I place the ferrite antenna close to a long wire, my coax going to a 2m+70cm J-Pole, WBAL comes in much stronger and closer to 900 than to 700. If I use only the built in ferrite antenna then WBAL is louder closer to 700 than 900.

So, I'm assuming a long wire antenna would also help.

Question, since WBAL is coming in between 700 and 900 when it should be in the 1090 range does this mean I placed one too many or one too few loops on the ferrite?

Hey I found this: https://goodcalculators.com/resonant-frequency-calculator/

This shows if the cap is at 100 pf and the inductor at 350 µH the Resonant freq (Rf) is ~850 KHz, if the inductor is 300 µH then the Rf ~ 918 KHz so if my Rf is too low on the dial it means I need less inductance and that means fewer loops around the ferrite. Fewer loops == lower inductance.

73 de KE3FL,
Phil
-----


Philip Karras <ke3fl@...>
 

Hi Curt,

Yep, that's the plan. Make simple mods first - Think I'll shorten the loop a bit & see if that helps even more than bending it flat to the board to get it away from the loopstick,

Then add more loops, one mod suggested ~ 72 loops & the tuner would then match up better to the printed frequencies. That will be the next mod I try.

73 de KE3FL,
Phil
ARRL OES, ORS, & VE
ARRL Life Member


On Friday, February 12, 2021, 3:13:02 PM EST, Curt via groups.io <wb8yyy@...> wrote:


Phil


These receivers using regeneration have different physics. You should not need more antenna, a loopstick will receive AM stations by itself over hundreds of miles at night.

Also better to have less coupling between the antenna and regeneration circuitry. Counter intuitive but true. Tuning is sharper with less signal coupled in, and the regeneration makes up for it. Patiently try less coupling. You want higher Q to get better selectivity.

My own AM regen is different, it uses a tube at 12 volts only on the plate. Like n3sb reports for his Murania, it pulls in dx at night. I also have a homebrew ozark patrol here, and a few other regens.

I did run across a blog discussing a modified murania, but get your stock radio working better with some adjustments.

Curt