Re: Problems, now that the radio is completed


Dave Benson
 

Charles-

1) Do you recall what frequency first came up when you first went into cal mode? The adjustment range is presently +/- 2.56 kHz.

2) The goal is 800 Hz. I assume you mean that the pitch is too high, which means the oscillator frequency is too high.  You should also be able to verify the frequency on another receiver - it should be at approximately 5185.9 kHz.  I'd suggest visually inspecting the capacitor values for that BFO circuit- let me know.

3) The gain control has an adjustment range in the low 30s (in dB). It's there to prevent front-end overload, and also mitigates item 4)

4) Audio screech: I had tried putting limiting diodes in the AF final. As they began conducting on large signals, they significantly detuned the bandpass function. Perhaps the most practical solution replaces the NE5532 with a (DIP) TLV2462. This raises the amp's internal current-limiting threshold from 34 mA (typ) to 80 mA. In simpler terms, that's about 8 dB more audio headroom.

5) I've been informed it's actually mode B, and confusion over that seems widespread.  It was mode A originally and a firmware revision changed that. This an 'action item' for me- I need to establish a way to choose either one on a one-time basis and retain it in EEPROM- along with the paddle reverse.

You can keep the rig permanently in Straight Key mode with a monaural plug- left in permanently. It should then 'pass through' the signal from an external keyer.
I don't envision offering it as a menu choice.

PA ruggedness:  I've built three Hilltoppers and at least that many predecessor designs using the 3xBS170 PA scheme. I haven't lost any PAs during boneheaded key-down mishaps. They seem to be pretty rugged. 

73- Dave, K1SWL
 

On Wed, Apr 11, 2018 at 9:30 PM, Charles W. Powell via Groups.Io <doctorcwp@...> wrote:
First, the radio sounds great and it seems to put out at least 5 watts, but there are a few problems I have encountered.

  1. After trying to match the frequency with the Cal jumper in place, the radio is again off frequency after I power cycle it. (about 1.2 KHz high - I can live with that.)
  2. The BFO is about 400 Hz too high (or 600 if the goal is a BFO frequency of 800 Hz.)  My KX2 is set at 600 Hz which appears to be around the peak of the passband on the Hilltopper.  If I try to adjust further, the BFO frequency merely starts to climb higher, and farther away from the desired frequency.  The trimmer cap I think was all the way down tight.  Which way does the trimmer go?  Increase or decrease capacitance?
  3. The gain control doesn't seem to do much.  That may have to do with proximity to the transmitter, but it seems it should do something.
  4. If you overload the front end of the receiver, it throws it into wild oscillation in the ear buds. OUCH!
  5. I am useless with iambic mode A. I simply can't use it after 35 years of iambic mode B and self-completing characters. Is there a way to permanently set the radio for straight key use? (Maybe short the outer ring to ground?)  Because of my other radios I do not have the ring connected (Elecrafts don't like it, except the K2.)
At a minimum, I must get the BFO frequency in the right place to try it in the field.

One more thing - how tolerant is the final to bone headed accidental keying without a load?  Haven't blown anything yet, but not wanting to do so either!

Oh great gurus of the Hilltopper, where should I go first?

72,

Charles


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