Hello Jim. . .

  I realize I have not built or seen the schematic of this radio (Yet). Because I just got through ordering 2 of them.
But. . .

For a tuned circuit, the more inductance you add, the lower the frequency. . .

Thus, you adding of 15 turns on top of a existing coil that is made for 1.6 mhz should LOWER the frequency,
instead of raising the frequency.  I would think that you would want to take the existing coil, unwrap about
X number of turns, and tap on to that point, then rewrap the coil back up. .  .
Placing a switch that excites the tapped point, and when turned off, uses the whole coil.

Please forgive me if I am wrong... Especially since I have not built or have the schematic in front of me!

Dwayne (Ka0aam)



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On Tue, 10/23/18, Jim WB2LHP in MI <jmarco1955@...> wrote:

 Subject: Re: [4SQRP] Murania on 5 MHz?
 To: main@4sqrp.groups.io
 Date: Tuesday, October 23, 2018, 2:52 PM

 Hi
 Dave...The short answer is "maybe"...
  I've been thinking about this
 myself...According to the data sheet, the TA7642 tops out at
 about 3MHz but I have read where people have used them at
 frequencies up to 10MHz...Here's a possible scenario you
 can try...
  If you are
 using the original 37-turn coil, you can add another 14
 turns to the coil and use the old end as a center tap...This
 creates a second winding of around 15uH...Depending on which
 coil you short out, you will get two tuning ranges...One for
 the AM broadcast band, the other for roughly 1800KHz to
 6MHz...I haven't tried this myself but it should
 work...
  Jim
 WB2LHP
 On Tue, Oct
 23, 2018 at 2:43 PM Dave Redfearn <n4elm@...>
 wrote:
 Would it
 be practical to mod the Murania to tune between 5 & 6
 MHz?
 73 - Dave, N4ELM