<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-08-25</periodOfReport>

    <issuer>
        <issuerCik>0000039020</issuerCik>
        <issuerName>FREQUENCY ELECTRONICS INC</issuerName>
        <issuerTradingSymbol>FEIM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001539953</rptOwnerCik>
            <rptOwnerName>Privet Fund Management LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>79 WEST PACES FERRY RD, SUITE 200B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30305</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>See Explanation of Responses</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001414517</rptOwnerCik>
            <rptOwnerName>Privet Fund LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>79 WEST PACES FERRY RD, SUITE 200B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30305</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>See Explanation of Responses</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001363032</rptOwnerCik>
            <rptOwnerName>Levenson Ryan</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>79 WEST PACES FERRY RD, SUITE 200B</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30305</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>See Explanation of Responses</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-08-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5178</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.87</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>975648</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Privet Fund LP</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-08-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>14516</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.96</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>990164</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Privet Fund LP</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>53783</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This report is filed jointly by Privet Fund LP, Privet Fund Management LLC and Ryan Levenson (collectively, the &quot;Reporting Persons&quot;).  The Reporting Persons are filing this report because each of the Reporting Persons may be deemed to be a member of a Section 13(d) group disclosed in the Schedule 13D and any amendments thereto filed on behalf of the Reporting Persons and the other members of such group.  As of July 6, 2016, the members of this Section 13(d) group collectively owned more than 10% of the Issuer's outstanding shares of Common Stock.  Each of the Reporting Persons disclaims beneficial ownership of the shares of Common Stock held by the other members of such Section 13(d) group except to the extent of his or its pecuniary interest therein.</footnote>
        <footnote id="F2">As of August 29, 2016, (i) 990,164 shares were owned directly by Privet Fund LP and indirectly by Privet Fund Management LLC and Ryan Levenson, and (ii) 53,783 shares were owned directly by Privet Fund Management LLC and indirectly by Ryan Levenson.</footnote>
        <footnote id="F3">The price reported in Column 4 is a weighted average price. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, further information regarding the number of shares purchased at each separate price within the range set forth in footnotes (4) and (5) to this Form 4.</footnote>
        <footnote id="F4">These shares were purchased in multiple transactions at prices ranging from $10.59 to $11.00, inclusive.</footnote>
        <footnote id="F5">These shares were purchased in multiple transactions at prices ranging from $10.78 to $11.00, inclusive.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Ryan Levenson</signatureName>
        <signatureDate>2016-08-29</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ryan Levenson, Managing Member, on behalf of Privet Fund Management LLC</signatureName>
        <signatureDate>2016-08-29</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ryan Levenson, Managing Member, on behalf of Privet Fund Management LLC, General Partner, on behalf of Privet Fund LP</signatureName>
        <signatureDate>2016-08-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
