Browning eagle mark 3

[vswr]

There were 2 crystals and a spdt switch installed in my txer. After doing some math, I found that they replaced 2 of the existing crystals to add in the extra channels to above 40 but howbit was broadbanded I think all they did was bypass the 2k plate resistor which I pulled. But 26, 31 and 36 would have to be slid into by the built in vfo on the rig I'm guessing. I pulled them out to put the radio txer back to its original condition. Now I need to plug that hole somehow. The 2 crystals were painted over do that the freqs would not be seen. I did manage to see that they came from Jan crystals who I think are out of biz. These are great radios.

 

[nomadradio]

There are three oscillator circuits in the Mark 3 SSB transmitter. One set of 23 16 MHz crystals, one for each channel. One set of three for the carrier feeds into the sideband modulator. For AM, this feeds directly into the sideband filter. One crystal for upper, one for lower and one for AM. But the 23 channel crystals can't be shifted up and down to match the carrier frequency for each mode. A second set of three crystals just over 5 MHz gets mixed with the 16 MHz channel crystals. These three crystals' frequencies are spaced apart the opposite 1.5 kHz jump that the three carrier crystals. The resulting 21 MHz you get from mixing the 16 MHz channel crystal and the 5 MHz offset crystal gets shifted when you change mode to keep the transmitter on the channel center for all three modes. Just one problem. This "offset" crystal oscillator feeds directly into an incredibly narrow-banded tuned circuit, T6. And this offset crystal is the one they chose for shifting the radio up 30 channels. It mixes with the 23 channel crystals, so "voila", 23 new channels with one crystal. Of course it only works on AM. You would need three of these to also get sideband.

But there's a fatal flaw. That narrowbanded coil T6 is a bottleneck. Peak it for the normal 23 channels and the uppers are really weak. Peak it for upper channels and 1-23 will be incredibly weak. Set the slug betwen the two peaks and all 46 channels will be wimpy.

We tried some tricks to get around this, but none of them were stable or reliable enough to be commercial quality. Dern!

You're not sacrificing anything worth caring about putting it back to stock.

I do remember one guy's fix for this dilemma. He took T6 and mounted it on its side, with the alignment hole pointing to the front. He drilled a hole in the front panel aligned with T6's slug and poked an alignment tool in so he could re-tweak T6 for either uppers or normal channels. It worked, but it also wore out the core in T6 before too long. With no remaining threads, the slug just sorta slid in and out.

Had to give the guy points for creativity, even if his fix had a fatal flaw.

73

 

[vswr]

There are three oscillator circuits in the Mark 3 SSB transmitter. One set of 23 16 MHz crystals, one for each channel. One set of three for the carrier feeds into the sideband modulator. For AM, this feeds directly into the sideband filter. One crystal for upper, one for lower and one for AM. But the 23 channel crystals can't be shifted up and down to match the carrier frequency for each mode. A second set of three crystals just over 5 MHz gets mixed with the 16 MHz channel crystals. These three crystals' frequencies are spaced apart the opposite 1.5 kHz jump that the three carrier crystals. The resulting 21 MHz you get from mixing the 16 MHz channel crystal and the 5 MHz offset crystal gets shifted when you change mode to keep the transmitter on the channel center for all three modes. Just one problem. This "offset" crystal oscillator feeds directly into an incredibly narrow-banded tuned circuit, T6. And this offset crystal is the one they chose for shifting the radio up 30 channels. It mixes with the 23 channel crystals, so "voila", 23 new channels with one crystal. Of course it only works on AM. You would need three of these to also get sideband.

But there's a fatal flaw. That narrowbanded coil T6 is a bottleneck. Peak it for the normal 23 channels and the uppers are really weak. Peak it for upper channels and 1-23 will be incredibly weak. Set the slug betwen the two peaks and all 46 channels will be wimpy.

We tried some tricks to get around this, but none of them were stable or reliable enough to be commercial quality. Dern!

You're not sacrificing anything worth caring about putting it back to stock.

I do remember one guy's fix for this dilemma. He took T6 and mounted it on its side, with the alignment hole pointing to the front. He drilled a hole in the front panel aligned with T6's slug and poked an alignment tool in so he could re-tweak T6 for either uppers or normal channels. It worked, but it also wore out the core in T6 before too long. With no remaining threads, the slug just sorta slid in and out.

Had to give the guy points for creativity, even if his fix had a fatal flaw.

73

 

[vswr]

Those coil cans are just like the ones in my midnight spevial and gemtronics 5000. Lousy slug threads. Worse is that the company that made those chassis used a horrible paint to seal them in place which made them near impossible to free up without thevrisk of breaking the tuning slug. The idea he had was a great preliminary if it was tuning only 1 slug. 73s

 

[vswr]

There are three oscillator circuits in the Mark 3 SSB transmitter. One set of 23 16 MHz crystals, one for each channel. One set of three for the carrier feeds into the sideband modulator. For AM, this feeds directly into the sideband filter. One crystal for upper, one for lower and one for AM. But the 23 channel crystals can't be shifted up and down to match the carrier frequency for each mode. A second set of three crystals just over 5 MHz gets mixed with the 16 MHz channel crystals. These three crystals' frequencies are spaced apart the opposite 1.5 kHz jump that the three carrier crystals. The resulting 21 MHz you get from mixing the 16 MHz channel crystal and the 5 MHz offset crystal gets shifted when you change mode to keep the transmitter on the channel center for all three modes. Just one problem. This "offset" crystal oscillator feeds directly into an incredibly narrow-banded tuned circuit, T6. And this offset crystal is the one they chose for shifting the radio up 30 channels. It mixes with the 23 channel crystals, so "voila", 23 new channels with one crystal. Of course it only works on AM. You would need three of these to also get sideband.

But there's a fatal flaw. That narrowbanded coil T6 is a bottleneck. Peak it for the normal 23 channels and the uppers are really weak. Peak it for upper channels and 1-23 will be incredibly weak. Set the slug betwen the two peaks and all 46 channels will be wimpy.

We tried some tricks to get around this, but none of them were stable or reliable enough to be commercial quality. Dern!

You're not sacrificing anything worth caring about putting it back to stock.

I do remember one guy's fix for this dilemma. He took T6 and mounted it on its side, with the alignment hole pointing to the front. He drilled a hole in the front panel aligned with T6's slug and poked an alignment tool in so he could re-tweak T6 for either uppers or normal channels. It worked, but it also wore out the core in T6 before too long. With no remaining threads, the slug just sorta slid in and out.

Had to give the guy points for creativity, even if his fix had a fatal flaw.

73

On my txer, the mod would switch in the 5 mhz crystals for am and lsb to a slightly higher set that would add in the channels from 24 to 40 and beyond. It made channel 2 into channel 24, 3 into 25 and then skipped 26. Pick up again at 27 through 30, skip 31 pick back up at 32, skip 36, pick up 37 through to 40 and above How it was broadbanded is anyone's guess. To get power over 23 he used the 2k plate resistor strapping mod. I pulled that all out. The txer final had no output so I couldnt test much other than voltages which are good. Gonna start scoping to check my oscillators. Just been too busy with summer chores. 73s