Rice boxes on AM - Icom 7300?

Discussion in 'Amplitude Modulation' started by W8EJO, Apr 18, 2016.

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  1. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Wow... "plastic radio"? Those who get offended by that must be pretty soft.
    Here in the Big Apple, dozens of different ethnic groups are packed in tightly (and that's fun). We have epithets aplenty for each other and everything! It's a tension releaser. :D
    N6YW likes this.
  2. W8EJO

    W8EJO Ham Member QRZ Page

    Not to get back on subject but -

    Has anyone done N1GPT's TS-850 AM mods?

    He says the mods result in: " AM transmit frequency response should be nearly flat from 20Hz up to 10Khz. This is substantially better than even the TS-950SDX operating in HiFi AM mode"

    I have e-mailed him to ask if he has any audio samples he could share.
  3. K5UJ

    K5UJ Ham Member QRZ Page

    I've been party to something similar with a FT1000MP. I think all the old analog plastic radios have the same basic procedure, which is to bypass the mic input by feeding the line level audio to the balanced modulator directly via a .1 or maybe .01 cap and isolation transformer, and pulling the 455 kc IF filter and jumpering the slot with a wire. In AM mode, there's usually a single filter in the signal path, often 6 kc (which partly accounts for the poor audio) and with that out of the picture and the mic. input bypassed, the rig will pass everything from almost zero to well over 10 kc.

  4. KM1H

    KM1H Ham Member QRZ Page

    I picked up my 75A4 with 3 filters, reduction knob and near mint condition for $200 in 64; still use it but it is showing its age. I could still buy NIB glass TX tubes: 100TH, 250TH, 304TL. 6C21, 810, 813, 814, 828, 845, 8000, 8005, etc, etc for $5-10 as little as 5-10 years ago before the Audiophools ruined the market.
    N6YW likes this.
  5. KA0KA

    KA0KA Ham Member QRZ Page

    Actually you may want to see my http://www.ka0ka.com TS-850 site where the original mods are for this, my 850 does 20Hz-10KHz in audio if desired, the RX is flat from down to 20Hz to what ever I put the top end at via the 883 IF filters. Great rig for both AM and ESSB with DSP-100 via Jensen transformer line level input.

    Use of a scope is mandatory for AM I listen to the demodulated RF and look at the XY mode on the scope for amp linearity via my Splatter View 5K. DSC02841.JPG DSC02844.JPG
  6. KA0KA

    KA0KA Ham Member QRZ Page

    You should just use WWV on 20 or 25MHz to do your own check, the higher in frequency you go the higher PPM the error will be so you can cal to that! I installed a VCTCXO in my TS-850/DSP-100 combo it was the best thing I ever did, rock solid netted into WWV on 20MHz! I use the RXer in Double Side Band for best results. See my pic below...

  7. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    Thanks for posting this response!
    I have owned nearly every modern radio made in the last 40 years, but the exception is the TS-850.
    I have repaired a couple of them for friends and used them on field day, GREAT CW rig btw.
    You have sparked the interest in getting one again, as I have been wanting one for a long time,
    but never got around to it.
    Perhaps you could share some more insight on this radio and a buyers guide, serial numbers etc.
    Thanks again! Great stuff.
    Billy N6YW
  8. N2DTS

    N2DTS Ham Member QRZ Page

    I have been looking at utube video's of the 7300 and it looks like a very good radio for a low price, now down to $1399.00.
    I have been resisting getting one, but I suppose its good to have an all mode all band rig with a built in tuna.
    Put up an alpha delta lb plus and have 160 to 10 meters.
    The alpha delta antenna should be ok at 100 watts, they melt if you run much above that...

    The price is what really makes it seem great, for such good performance and features, its hard to pay for anything else.
    Any of the elecraft radios will be a lot more after you add the options, the flex and Anan radios are 2 or 3x the price, may not have a tuna and need the computer.
    N6YW likes this.
  9. N2DTS

    N2DTS Ham Member QRZ Page

    ON a side note, new firmware allows the KX2 to send and receive AM.
    80 to 10 meters, 10 watts pep output, you can use it like a walkie talkie.

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